Tag Archives: Mesoscale and Nanoscale Physics

An rf Quantum Capacitance Parametric Amplifier [CL]

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http://arxiv.org/abs/2304.13227


We demonstrate a radio-frequency parametric amplifier that exploits the gate-tunable quantum capacitance of an ultra high mobility two dimensional electron gas (2DEG) in a GaAs heterostructure at cryogenic temperatures. The prototype narrowband amplifier exhibits a gain greater than 20 dB up to an input power of – 66 dBm (1 dB compression), and a noise temperature TN of 1.3 K at 370 MHz. In contrast to superconducting amplifiers, the quantum capacitance parametric amplifier (QCPA) is operable at tesla-scale magnetic fields and temperatures ranging from milli kelvin to a few kelvin. These attributes, together with its low power (microwatt) operation when compared to conventional transistor amplifiers, suggest the QCPA may find utility in enabling on-chip integrated readout circuits for semiconductor qubits or in the context of space transceivers and radio astronomy instruments.

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A. Kass, C. Jin, J. Watson, et. al.
Thu, 27 Apr 23
49/78

Comments: N/A

A systematic formulation of chiral anomalous magnetohydrodynamics [CL]

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http://arxiv.org/abs/2212.09757


We present a new way of deriving effective theories of dynamical electromagnetic fields in general media. It can be used to give a systematic formulation of magnetohydrodynamics (MHD) with strong magnetic fields, including systems with chiral matter and Adler-Bell-Jackiw (ABJ) anomaly. We work in the regime in which velocity and temperature fluctuations can be neglected. The resulting chiral anomalous MHD incorporates and generalizes the chiral magnetic effect, the chiral separation effect, the chiral electric separation effect, as well as recently derived strong-field MHD, all in a single coherent framework. At linearized level, the theory predicts that the chiral magnetic wave survives strong dynamical magnetic fields, and predicts the wave velocity. We also introduce a simple, but solvable nonlinear model to explore the fate of the chiral instability.

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M. Landry and H. Liu
Wed, 21 Dec 22
3/81

Comments: 22 pages

Dark Matter Direct Detection with Quantum Dots [CL]

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http://arxiv.org/abs/2208.05967


We propose using Quantum Dots as novel targets to probe sub-GeV dark matter-electron interactions. Quantum dots are nanocrystals of semiconducting material, which are commercially available, with gram-scale quantities suspended in liter-scale volumes of solvent. Quantum dots can be efficient scintillators, with near unity single-photon quantum yields, and their band-edge electronic properties are determined by their characteristic size, which can be precisely tuned. Examples include lead sulfide (PbS) and lead selenide (PbSe) quantum dots, which can be tuned to have sub-eV optical gaps. A dark-matter interaction can generate one or more electron-hole pairs (excitons), with the multi-exciton state decaying via the emission of two photons with an efficiency of about 10% of the single-photon quantum yield. An experimental setup using commercially available quantum dots and two photo-multiplier-tubes (PMTs) for detecting the coincident two-photon signal can already improve on existing dark-matter bounds, while using photodetectors with lower dark-count rates can improve on current constraints by orders of magnitude.

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C. Blanco, R. Essig, M. Fernandez-Serra, et. al.
Mon, 15 Aug 22
34/54

Comments: 12 pages, 7 figures ; Appendix 4 pages, 1 figure

Formation of Chiral Soliton Lattice [CL]

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http://arxiv.org/abs/2207.00212


The Chiral Soliton Lattice (CSL) is a lattice structure composed of domain walls aligned in parallel at equal intervals, which is energetically stable in the presence of a background magnetic field and a finite (baryon) chemical potential due to the topological term originated from the chiral anomaly. We study its formation from the vacuum state, with describing the CSL as a layer of domain-wall disks surrounded by the vortex or string loop, based on the Nambu-Goto-type effective theory. We show that the domain wall nucleates via quantum tunneling when the magnetic field is strong enough. We evaluate its nucleation rate and determine the critical magnetic field strength with which the nucleation rate is no longer exponentially suppressed. We apply this analysis to the neutral pion in the two-flavor QCD as well as the axion-like particles (ALPs) with a finite (baryon) chemical potential under an external magnetic field. In the former case, even though the CSL state is more energetically stable than the vacuum state and the nucleation rate becomes larger for sufficiently strong magnetic field, it cannot be large enough so that the nucleation of the domain walls is not exponentially suppressed and promoted, without suffering from the tachyonic instability of the charged pion fluctuations. In the latter case, we confirm that the effective interaction of the ALPs generically includes the topological term required for the CSL state to be energetically favored. We show that the ALP CSL formation is promoted if the magnetic field strength and the chemical potential of the system is slightly larger than the scale of the axion decay constant.

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T. Higaki, K. Kamada and K. Nishimura
Mon, 4 Jul 22
56/62

Comments: 21 pages, 5 figures

Birefringent Rydberg Dark Matter from Cosmic Dust [CL]

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http://arxiv.org/abs/2204.10908


A recently published study of dark matter in distant galaxies has found a direct interaction between unknown dark matter particles and ordinary galactic baryonic matter. It is proposed here that the dark matter is Rydberg Matter composed of water nanoclusters ejected from abundant amorphous water-ice-coated cosmic dust, leading to non-gravitational interactions with ordinary matter. This may also clarify recently observed CMB birefringence, suggesting possible new physics such as quintessence.

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K. Johnson
Tue, 26 Apr 22
25/74

Comments: 10 pages, 5 figures. arXiv admin note: substantial text overlap with arXiv:2012.12079

Unstable Nambu-Goldstone modes [CL]

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http://arxiv.org/abs/2203.02727


Nambu-Goldstone (NG) modes for 0-form and higher-form symmetries can become unstable in the presence of background fields. The examples include the instability of a photon with a time-dependent axion background or with a chirality imbalance, known as the chiral plasma instability, and the instability of a dynamical axion with a background electric field. We show that all these phenomena can be universally described by a symmetry algebra for 0-form and higher-form symmetries. We prove a counting rule for the number of unstable NG modes in terms of correlation functions of broken symmetry generators. Based on our unified description, we further give a simple new example where one of the NG modes associated with the spontaneous 0-form symmetry breaking $U(1) \times U(1) \to {1}$ becomes unstable.

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N. Yamamoto and R. Yokokura
Tue, 8 Mar 22
48/100

Comments: 8 pages

Theory of drain noise in high electron mobility transistors based on real-space transfer [CL]

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http://arxiv.org/abs/2108.03370


High electron mobility transistors are widely used as microwave amplifiers owing to their low microwave noise figure. Electronic noise in these devices is typically modeled by noise sources at the gate and drain. While consensus exists regarding the origin of the gate noise, that of drain noise is a topic of debate. Here, we report a theory of drain noise as a type of partition noise arising from real-space transfer of hot electrons from the channel to the barrier. The theory accounts for the magnitude and dependencies of the drain temperature and suggests strategies to realize devices with lower noise figure.

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I. Esho, A. Choi and A. Minnich
Wed, 11 Aug 21
32/72

Comments: N/A

Quasiballistic electron transport in cryogenic SiGe HBTs studied using an exact, semi-analytic solution to the Boltzmann equation [CL]

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http://arxiv.org/abs/2106.05374


Silicon-germanium heterojunction bipolar transistors (HBTs) are of interest as low-noise microwave amplifiers due to their competitive noise performance and low cost relative to III-V devices. The fundamental noise performance limits of HBTs are thus of interest, and several studies report that quasiballistic electron transport across the base is a mechanism leading to cryogenic non-ideal IV characteristics that affects these limits. However, this conclusion has not been rigorously tested against theoretical predictions because prior studies modeled electron transport with empirical approaches or approximate solutions of the Boltzmann equation. Here, we study non-diffusive transport in narrow-base SiGe HBTs using an exact, semi-analytic solution of the Boltzmann equation based on an asymptotic expansion approach. We find that the computed transport characteristics are inconsistent with experiment, implying that quasiballistic electron transport is unlikely to be the origin of cryogenic non-ideal IV characteristics. Our work helps to identify the mechanisms governing the lower limits of the microwave noise figure of cryogenic HBT amplifiers.

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N. Naik and A. Minnich
Mon, 14 Jun 21
37/58

Comments: N/A

Void defect induced magnetism and structure change of carbon materials-1, Graphene nano ribbon [CL]

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http://arxiv.org/abs/2104.09740


Void defect is a possible origin of ferromagnetic like feature of pure carbon material. Applying density functional theory to void defect induced graphene nano ribbon (GNR), a detailed relationship between multiple spin state and structure change was studied. An equitorial triangle of an initial initial void having six electrons is distorted to isosceles triangle by rebonding carbon atoms. Among possible spin states, the most stable state was Sz=2/2. The case of Sz=4/2 is remarkable that initial flat ribbon turned to three dimentional curled one having highly polarized spin configuration at ribbon edges. Total energy of Sz=4/2 was very close to that of Sz=2/2, which suggests coexistence of flat and curled ribbons. As a model of three dimensional graphite, bilayered AB stacked GNR was analyzed. Spin distribution was limited to the void created layer. Distributed void triangle show 60 degree clockwise rotation for differrent site void, which was consistent with experimental observation using the scanning tunneling microscope. (To be published on Journal of the Magnetic Society of Japan, 2021 )

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N. Ota and L. Nemes
Wed, 21 Apr 2021
12/72

Comments: 7 pages, 7 figures, 2 tables

Void defect induced magnetism and structure change of carbon material-3, Polycyclic aromatic hydrocarbon [GA]

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http://arxiv.org/abs/2104.09747


Void-defect induced magnetism of graphene molecule was recently reported in our previous paper of this series study. This paper investigated the case of hydrogenated graphene molecule, in chemical term, polycyclic aromatic hydrocarbon (PAH). Molecular infrared spectrum obtained by density functional theory was compared with astronomical observation. Void-defect on PAH caused serious structure change. Typical example of C23H12 had two carbon pentagon rings among hexagon networks. Stable spin state was non-magnetic singlet state. This is contrary to pure carbon case of C23, which show magnetic triplet state. It was discussed that Hydrogen played an important role to diminish magnetism by creating an SP3-bond among SP2-networks. Such a structure change affected molecular vibration and finally to photoemission spectrum in infrared region. The dication-C23H12 showed featured bands at 3.2, 6.3, 7.7, 8.6, 11.2, and 12.7 micrometer. It was surprising that those calculated bands coincided well with astronomically observed bands in many planetary nebulae. To confirm our study, large size molecule of C53H18 was studied. Calculation reproduced again similar astronomical bands. Also, small size molecule of C12H8 showed good coincidence with the spectrum observed for young stars. This paper would be the first report to indicate the specific PAH in space.

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N. Ota, A. Li and L. Nemes
Wed, 21 Apr 2021
38/72

Comments: 10 pages, 14 figures, 1 table

Void defect induced magnetism and structure change of carbon material-2, Graphene molecules [GA]

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http://arxiv.org/abs/2104.09745


Void-defect is a possible origin of ferromagnetic feature on pure carbon materials. In our previous paper, void-defect on graphene-nanoribbon show highly polarized spin configuration. In this paper, we studied cases for graphene molecules by quantum theory, by astronomical observation and by laboratory experiment. Model molecules for the density functional theory are graphene molecules of C23 and C53 induced by a void-defect. They have carbon pentagon ring within a hexagon network. Single void has three radical carbons, holding six spins. Those spins make several spin-states, which affects to molecular structure and molecular vibration, finally to infrared spectrum. The stable spin state was triplet, not singlet. This suggests magnetic pure carbon molecule. It was a surprise that those molecules show close infrared spectrum with astronomically observed one, especially observed on carbon rich planetary nebulae. We could assign major band at 18.9 micrometer, and sub-bands at 6.6, 7.0, 7.6, 8.1, 8.5, 9.0 and 17.4 micrometer. Also, calculated spectrum roughly coincides with that of laboratory experiment by the laser-induced carbon plasma, which is an analogy of cosmic carbon creation in interstellar space.

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N. Ota, A. Li, L. Nemes, et. al.
Wed, 21 Apr 2021
64/72

Comments: 9 pages, 6 figures, 1 table. arXiv admin note: text overlap with arXiv:2007.03862

Sensitive Superconducting Calorimeters for Dark Matter Search [CL]

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http://arxiv.org/abs/2101.08558


The composition of dark matter is one of the puzzling topics in astrophysics. Since, the existence of axions would fill this gap of knowledge, several experiments for the search of axions have been designed in the last twenty years. Among all the others, light shining through walls experiments promise to push the exclusion limits to lower energies. To this end, effort is put for the development of single-photon detectors operating at frequencies $<100$ Ghz. Here, we review recent advancements in superconducting single-photon detection. In particular, we present two sensors based on one-dimensional Josephson junctions with the capability to be in situ tuned by simple current bias: the nanoscale transition edge sensor (nano-TES) and the Josephson escape sensor (JES). These two sensors seem to be the perfect candidates for the realization of microwave light shining through walls (LSW) experiments, since they show unprecedented frequency resolutions of about 100 GHz and 2 GHz for the nano-TES and JES, respectively.

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F. Paolucci and F. Giazotto
Fri, 22 Jan 21
67/69

Comments: 15 pages, 7 figures. arXiv admin note: text overlap with arXiv:2011.08745

Axion assisted Schwinger effect [CL]

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http://arxiv.org/abs/2101.05192


We point out an enhancement of the pair production rate of charged fermions in a strong electric field in the presence of time dependent classical axion-like background field, which we call axion assisted Schwinger effect. While the standard Schwinger production rate is proportional to $\exp(-\pi(m^2+p_T^2 )/E)$, with $m$ and $p_T$ denoting the fermion mass and its momentum transverse to the electric field $E$, the axion assisted Schwinger effect can be enhanced at large momenta to $\exp(-\pi m^2/E)$. The origin of this enhancement is a coupling between the fermion spin and its momentum, induced by the axion velocity. As a non-trivial validation of our result, we show its invariance under field redefinitions associated with a chiral rotation and successfully reproduce the chiral anomaly equation in the presence of helical electric and magnetic fields. We comment on implications of this result for axion cosmology, focussing on axion inflation and axion dark matter detection.

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V. Domcke, Y. Ema and K. Mukaida
Thu, 14 Jan 21
7/79

Comments: 18 pages + appendices, 5 figures

Graphene Molecules Contributing to the Infrared Bands of Carbon Rich Planetary Nebulae [GA]

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http://arxiv.org/abs/2007.03862


It is well known since 2010 that fullerene C60 is widespread through the interstellar space. Also, it is well known that graphene is a source material for synthesizing fullerene. Here, we simply assume the occurrence of graphene in space. Infrared spectra of graphene molecules are calculated to compare both to astronomical observational spectra and to laboratory experimental one. Model molecules for DFT calculation are selected by one simple astronomical assumption, that is, single void creation on charge neutral graphene of C13, C24 and C54, resulting C12, C23 and C53. They have a carbon pentagon ring within a hexagon network. Different void positions should be classified as different species. In every species, single void has 3 radical carbons holding 6 spins. These spins select stable state by recombination of carbon atoms to reduce molecular energy, and to give infrared spectrum due to molecular vibration. It was found that stable spin state was the triplet, not singlet. Most of species show prominent infrared spectral features closely resembling the astronomically observed infrared emission seen in the carbon rich planetary nebulae of Tc1 and Lin49. We could assign major bands at 18.9 micrometer, and sub-bands at 6.6, 7.0, 7.6, 8.1, 8.5, 9.0 and 17.4 micrometer. It is interesting that those graphene species were also assigned in the laboratory experiments on laser-induced carbon plasmas, which are analogies of carbon cluster creation in space. The conclusion is that graphene molecules could potentially contribute to the infrared emission bands of carbon-rich planetary nebulae.

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N. Ota, A. Li, L. Nemes, et. al.
Thu, 9 Jul 20
21/70

Comments: 21 pages, 8 figures, 1 table, 1 appendix

Magnetic monopoles and fermion number violation in chiral matter [CL]

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http://arxiv.org/abs/2005.05028


We show that the presence of a magnetic monopole in position space gives rise to a violation of the fermion number conservation in chiral matter. Using the chiral kinetic theory, we derive a model-independent expression of such a violation in nonequilibrium many-body systems of chiral fermions. In local thermal equilibrium at finite temperature and chemical potential, in particular, this violation is proportional to the chemical potential with a topologically quantized coefficient. These consequences are due to the interplay between the Dirac monopole in position space and the Berry monopole in momentum space. Our mechanism can be applied to study the roles of magnetic monopoles in the nonequilibrium evolution of the early Universe.

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N. Yamamoto
Tue, 12 May 20
4/64

Comments: 5 pages

Nonlinear Effects in Superconducting Thin Film Microwave Resonators [CL]

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http://arxiv.org/abs/2001.02540


We discuss how reactive and dissipative non-linearities affect the intrinsic response of superconducting thin-film resonators. We explain how most, if not all, of the complex phenomena commonly seen can be described by a model in which the underlying resonance is a single-pole Lorentzian, but whose centre frequency and quality factor change as external parameters, such as readout power and frequency, are varied. What is seen during a vector-network-analyser measurement is series of samples taken from an ideal Lorentzian that is shifting and spreading as the readout frequency is changed. According to this model, it is perfectly proper to refer to, and measure, the resonant frequency and quality factor of the underlying resonance, even though the swept-frequency curves appear highly distorted and hysteretic. In those cases where the resonance curve is highly distorted, the specific shape of the trajectory in the Argand plane gives valuable insights into the second-order physical processes present. We discuss the formulation and consequences of this approach in the case of non-linear kinetic inductance, two-level-system loss, quasiparticle generation, and a generic model based on a power-law form. The generic model captures the key features of specific dissipative non-linearities, but additionally leads to insights into how general dissipative processes create characteristic forms in the Argand plane. We provide detailed formulations in each case, and indicate how they lead to the wide variety of phenomena commonly seen in experimental data. We also explain how the properties of the underlying resonance can be extracted from this data. Overall, our paper provides a self-contained compendium of behaviour that will help practitioners interpret and determine important parameters from distorted swept-frequency measurements.

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C. Thomas, S. Withington, Z. Sun, et. al.
Fri, 10 Jan 20
25/65

Comments: 55 pages, 15 figures

Chiral Anomaly, Schwinger Effect, Euler-Heisenberg Lagrangian, and application to axion inflation [CL]

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http://arxiv.org/abs/1910.01205


Particle production in strong electromagnetic fields is a recurring theme in solid state physics, heavy ion collisions, early universe cosmology and formal quantum field theory. In this paper we discuss the Dirac equation in a background of parallel electric and magnetic fields. We review the Schwinger particle production rate, clarify the emergence of the chiral anomaly equation and compute the induced current of charged fermions. We distinguish the contributions from non-perturbative particle production, from the running of the gauge coupling constant and from non-linearities in the effective QED Lagrangian, and clarify how these contributions arise within a single framework. We apply these results to axion inflation. A Chern-Simons coupling between the pseudoscalar particle driving cosmic inflaton and an abelian gauge group induces a dual production of gauge fields and charged fermions. We show that the resulting scalar and gravitational wave power spectra strongly depend on the fermion mass.

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V. Domcke, Y. Ema and K. Mukaida
Fri, 4 Oct 19
26/61

Comments: 45 pages, 9 figures

Tunable Antenna-Coupled Intersubband Terahertz (TACIT) Mixers: The Quantum Limit Without the Quantum Liquid [CL]

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http://arxiv.org/abs/1909.10664


At present, nearly quantum-limited heterodyne receivers for Terahertz (THz) frequencies require cooling to temperatures below 4K. We are working to build semiconductor-based “tunable antenna-coupled intersubband terahertz” (TACIT) heterodyne mixers for 1-5 THz. We predict that they can achieve single-sideband noise temperatures of a few hundred K with intermediate frequency (IF) bandwidth >10 GHz, while operating at lattice temperatures >20 K and requiring local oscillator (LO) power ~ 1 $\mu$W.

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M. Sherwin, C. Cates, B. Serapiglia, et. al.
Wed, 25 Sep 19
58/70

Comments: This paper was published in the Proceedings of the Far-IR, Submm, and mm Detector Technology Workshop, Monterey, CA (2002). The URL for the proceedings no longer exists, so this eprint is submitted here for public access. The eprint is identical to the version published in 2002. One correction is required: in Eq. (4): Gamma/(2pi), not Gamma(2*pi), is the HWHM of the intersubband transition

Nontrivial topology of the Alfvén continuum and topological origin of reversed-shear Alfvén eigenmodes [CL]

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http://arxiv.org/abs/1909.07910


In an inhomogeneous plasma, the ideal magnetohydrodynamics model gives rise to the Alfv\'{e}n continuum, consisting of non-square-integrable improper eigenfunctions. For a gravitating slab, we calculate a Chern number for the Alfv\'{e}n continuum on a given magnetic surface. For strong magnetic shear, the Chern number is equal to $\pm 1$, depending on the sign of the shear. By appeal to the bulk-boundary correspondence, this result suggests a topological character of the reversed-shear Alfv\'{e}n eigenmode, which has been observed in tokamaks and is radially localized to layers of zero magnetic shear. As a result, the reversed-shear Alfv\'{e}n eigenmode may be topologically robust to three-dimensional perturbations such as magnetic islands.

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J. Parker, J. Burby, J. Marston, et. al.
Wed, 18 Sep 19
19/64

Comments: 5 pages, 2 figures

Graphene-based Josephson junction microwave bolometer [CL]

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http://arxiv.org/abs/1909.05413


Sensitive microwave detectors are critical instruments in radioastronomy, dark matter axion searches, and superconducting quantum information science. The conventional strategy towards higher-sensitivity bolometry is to nanofabricate an ever-smaller device to augment the thermal response. However, this direction is increasingly more difficult to obtain efficient photon coupling and maintain the material properties in a device with a large surface-to-volume ratio. Here we advance this concept to an ultimately thin bolometric sensor based on monolayer graphene. To utilize its minute electronic specific heat and thermal conductivity, we develop a superconductor-graphene-superconductor (SGS) Josephson junction bolometer embedded in a microwave resonator of resonant frequency 7.9 GHz with over 99\% coupling efficiency. From the dependence of the Josephson switching current on the operating temperature, charge density, input power, and frequency, we demonstrate a noise equivalent power (NEP) of 7 $\times 10^{-19}$ W/Hz$^{1/2}$, corresponding to an energy resolution of one single photon at 32 GHz and reaching the fundamental limit imposed by intrinsic thermal fluctuation at 0.19 K.

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G. Lee, D. Efetov, L. Ranzani, et. al.
Fri, 13 Sep 19
58/70

Comments: 8 pages, 4 figures

Towards quantum-limited coherent detection of terahertz waves in charge-neutral graphene [CL]

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http://arxiv.org/abs/1904.03247


Spectacular advances in heterodyne astronomy with both the Herschel Space Observatory and Stratospheric Observatory for Far Infrared Astronomy (SOFIA) have been largely due to breakthroughs in detector technology. In order to exploit the full capacity of future THz telescope space missions (e.g. Origins Space Telescope), new concepts of THz coherent receivers are needed, providing larger bandwidths and imaging capabilities with multi-pixel focal plane heterodyne arrays. Here we show that graphene, uniformly doped to the Dirac point, enables highly sensitive and wideband coherent detection of THz signals. With material resistance dominated by quantum localization, and thermal relaxation governed by electron diffusion, proof-of-concept graphene bolometers demonstrate a gain bandwidth of 8 GHz and a mixer noise temperature of 475 K, limited by residual thermal background in our setup. An optimized device will result in a mixer noise temperature as low as 36 K, with the gain bandwidth exceeding 20 GHz, and a Local Oscillator power lower than 100 pW. In conjunction with the emerging quantum-limited amplifiers at the intermediate frequency, our approach promises quantum-limited sensing in the THz domain, potentially surpassing superconducting technologies, particularly for large heterodyne arrays.

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S. Lara-Avila, A. Danilov, D. Golubev, et. al.
Mon, 5 Aug 19
27/53

Comments: 15 pages, 4 figures

Quantum interference between light sources separated by 150 million kilometers [CL]

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http://arxiv.org/abs/1905.02868


We report an experiment to test quantum interference, entanglement and nonlocality using two dissimilar photon sources, the Sun and a semiconductor quantum dot on the Earth, which are separated by 150 million kilometers. By making the otherwise vastly distinct photons indistinguishable all degrees of freedom, we observe time-resolved two-photon quantum interference with a raw visibility of 0.796(17), well above the 0.5 classical limit, providing the first evidence of quantum nature of thermal light. Further, using the photons with no common history, we demonstrate post-selected two-photon entanglement with a state fidelity of 0.826(24), and a violation of Bell’s inequality by 2.20(6).

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Y. Deng, H. Wang, X. Ding, et. al.
Thu, 9 May 19
32/59

Comments: 16 pages, 5 figures

Graphene Molecule Compared With Fullerene C60 As Circumstellar Carbon Dust Of Planetary Nebula [GA]

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http://arxiv.org/abs/1904.10140


It had been understood that astronomically observed infrared spectrum of carbon rich planetary nebula as like Tc 1 and Lin 49 comes from fullerene (C60). Also, it is well known that graphene is a raw material for synthesizing fullerene. This study seeks some capability of graphene based on the quantum-chemical DFT calculation. It was demonstrated that graphene plays major role rather than fullerene. We applied two astrophysical conditions, which are void creation by high speed proton and photo-ionization by the central star. Model molecule was ionized void-graphene (C23) having one carbon pentagon combined with hexagons. By molecular vibrational analysis, we could reproduce six major bands from 6 to 9 micrometer, large peak at 12.8, and largest peak at 19.0. Also, many minor bands could be reproduced from 6 to 38 micrometer. Also, deeply void induced molecules (C22) and (C21) could support observed bands.

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N. Ota
Wed, 24 Apr 19
48/51

Comments: 9 pages, 7 figures

Properties of magnetized Coulomb crystals of ions with polarizable electron background [CL]

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http://arxiv.org/abs/1901.10809


We have studied phonon and thermodynamic properties of a body-centered cubic (bcc) Coulomb crystal of ions with weakly polarized electron background in a uniform magnetic field ${\bf B}$. At $B=0$ the difference between phonon moments calculated using the Thomas-Fermi (TF) and random phase (RPA) approximations is always less than one percent and for description of phonon properties of a crystal TF formalism was used. This formalism was successfully applied to investigate thermodynamic properties of magnetized Coulomb crystals. It was shown that the influence of the polarization of the electron background is significant only at $\kappa_{\rm TF}a > 0.1$ and $T \ll T_{\rm p}(1+h^2)^{-1/2}$, where $\kappa_{\rm TF}$ is the Thomas-Fermi wavenumber, $a$ is the ion sphere radius, $T_{\rm p}\equiv\hbar \omega_{\rm p}$ is the ion plasma temperature, $h\equiv \omega_B/\omega_{\rm p}$, $\omega_B$ is the ion cyclotron frequency and $\omega_{\rm p}$ is the ion plasma frequency.

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A. Kozhberov
Thu, 31 Jan 19
38/59

Comments: 5 pages, 4 figures

Chiral Anomaly and Schwinger Effect in Non-Abelian Gauge Theories [CL]

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http://arxiv.org/abs/1812.08021


We study the production of chiral fermions in a background of a strong non-abelian gauge field with a non-vanishing Chern-Pontryagin density. We discuss both pair production analogous to the Schwinger effect as well as asymmetric production through the chiral anomaly, sourced by the Chern-Pontryagin density. In abelian gauge theories one may nicely understand these processes by considering that the fermion dispersion relation forms discrete Landau levels. Here we extend this analysis to a non-abelian gauge theory, considering an intrinsically non-abelian isotropic and homogeneous SU(2) gauge field background with a non-vanishing Chern-Pontryagin density. We show that the asymmetric fermion production, together with a non-trivial vacuum contribution, correctly reproduces the chiral anomaly. This indicates that the usual vacuum subtraction scheme, imposing normal ordering, fails in this case. As a concrete example of this gauge field background, we consider chromo-natural inflation. Applying our analysis to this particular model, we compute the backreaction of the generated fermions on the gauge field background. This backreaction receives contributions both from the vacuum through a Coleman-Weinberg-type correction and from the fermion excitations through an induced current.

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V. Domcke, Y. Ema, K. Mukaida, et. al.
Fri, 21 Dec 18
71/72

Comments: 26 pages + appendices, 2 figures

Astronomical Infrared Spectrum of Planetary Nebula Lin49 and Tc1 Identified by Ionized Polycyclic-Pure-Carbon C23 and C60 [GA]

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http://arxiv.org/abs/1811.05043


Astronomical dust molecule of carbon-rich nebula-Lin49 and nebula-Tc1 could be identified to be polycyclic-pure-carbon C23 by the quantum-chemical calculation. Two driving forces were assumed. One is high speed proton attack on coronene-C24H12, which created void-induced C23H12. Another is high energy photon irradiation, which brought deep photo-ionization and finally caused dehydrogenation to be C23. Infrared spectrum calculation show that a set of ionized C23 (neutral, mono, and di-cation) could reproduce observed many peaks of 28 bands at wavelength from 6 to 38 micrometer. Previously predicted neutral fullerene-C60 could partially reproduce observed spectrum by 5 bands. Also, we tried calculation on ionized-C60, which show fairly good coincidence with observed 10 bands

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N. Ota
Wed, 14 Nov 18
2/75

Comments: 9 pages, 10 figures

Astronomical Creation of Cyclic-C3H2 and Chain-C3 Due to Interstellar Deep Photoionization [GA]

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http://arxiv.org/abs/1810.06006


Astronomical evolution mechanism of small size polycyclic aromatic hydrocarbon (PAH) was analyzed using the first principles quantum-chemical calculation. Starting model molecule was benzene (C6H6), which would be transformed to (C5H5) due to carbon void created by interstellar high speed proton attack. In a protoplanetary disk around a young star, molecules would be illuminated by high energy photon and ionized to be cationic-(C5H5). Calculation shows that from neutral to tri-cation, molecule keeps original configuration. At a step of sixth cation, there occurs surprising creation of cyclic-C3H2, which is the smallest PAH. Astronomical cyclic-C3H2 had been identified by radio astronomy. Deep photoionization of cyclic-C3H2 brings successive molecular change. Neutral and mono-cation keep cyclic configuration. At a step of di-cation, molecule was transformed to aliphatic chain-C3H2. Finally, chain-C3H2 was decomposed to pure carbon chain-C3 and two hydrogen atoms. Calculated infrared spectrum of those molecules was applied to observed spectrum of Herbig Ae young stars. Observed infrared spectrum could be partially explained by small molecules. Meanwhile, excellent coincidence was obtained by applying a larger molecules as like (C23H12)2+ or (C12H8)2+. Infrared observation is suitable for larger molecules and radio astronomy for smaller asymmetric molecules. It should be noted that these molecules could be identified in a natural way introducing two astronomical phenomena, that is, void-induced molecular deformation and deep photoionization.

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N. Ota
Tue, 16 Oct 18
43/83

Comments: 11 pages, 13 figures, 1 table

Astronomical Quantum-chemical Origin of Ubiquitously Observed Interstellar Infrared Spectrum due to Polycyclic Aromatic Hydrocarbon [GA]

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http://arxiv.org/abs/1808.01070


Interstellar infrared observation shows featured spectrum due to polycyclic aromatic hydrocarbon (PAH)at wavelength 3.3,6.2,7.6,7.8,8.6,and 11.3 micrometer,which are ubiquitously observed in many astronomical dust clouds and galaxies. Our previous first principles calculation revieled that viod induced coronene (C23H12)2+ and circumcoronene (C53H18)1+ could reproduce such spectrum very well. In this study, quantum-mechanic origin was studied through atomic configuration change and atomic vibration mode analysis. By a high speed particle attack, carbon void would be introduced in PAH. Molecular configuration was deformed by the Jahn-Teller quantum effect. Carbon SP3 local bond was created among SP2 graphene like carbon network. Also, carbon tetrahedron local structure was created. Such peculiar structure is the quantum origin. Those metamorphosed molecules would be photo-ionized by the central star strong photon irradiation resulting cation molecules. Atomic vibration mode of cation molecule (C23H12)2+ was compared with that of neutral one (C23H12). At 3.3 micrometer, both molecules show show C-H stretching mode and give fairly large infrared intensity. At 6.2,7.6,7.8, and 8.6 micrometer bands, cation molecule show complex C-C stretching and shrinking mixing modes and remain large infrared emission. Whereas, neutral molecule gives harmonic motion, which cancelles each other resulting very small infrared intensity. At 11.3 micrometer, both neutral and cation molecules show C-H bending motion perpendicular to a molecular plane, which contributes to strong emission. Actual observed spectrum would be a sum of such quantum-mechanic origined molecules.

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N. Ota
Mon, 6 Aug 18
14/33

Comments: 13pages, 10 figures, 1 table, 6 appendix

Ion implantation in nanodiamonds: size effect and energy dependence [CL]

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http://arxiv.org/abs/1803.09081


Nanoparticles are ubiquitous in nature and are increasingly important for technology. They are subject to bombardment by ionizing radiation in a diverse range of environments. In particular, nanodiamonds represent a variety of nanoparticles of significant fundamental and applied interest. Here we present a combined experimental and computational study of the behaviour of nanodiamonds under irradiation by xenon ions. Unexpectedly, we observed a pronounced size effect on the radiation resistance of the nanodiamonds: particles larger than 8 nm behave similarly to macroscopic diamond (i.e. characterized by high radiation resistance) whereas smaller particles can be completely destroyed by a single impact from an ion in a defined energy range. This latter observation is explained by extreme heating of the nanodiamonds by the penetrating ion. The obtained results are not limited to nanodiamonds, making them of interest for several fields, putting constraints on processes for the controlled modification of nanodiamonds, on the survival of dust in astrophysical environments, and on the behaviour of actinides released from nuclear waste into the environment.

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A. Shiryaev, J. Hinks, N. Marks, et. al.
Wed, 28 Mar 18
22/148

Comments: Supplementray information is at: doi:10.1038/s41598-018-23434-y

Analyzing interstellar infrared spectrum by circumcoronene (C54H18) related molecules [GA]

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http://arxiv.org/abs/1801.06305


It is very important to identify carrier molecules of astronomical interstellar infrared spectrum (IR) to understand chemical evolution step of polycyclic aromatic hydrocarbon (PAH) in the universe. In our previous study, it was suggested that coronene (C24H12) related PAH could reproduce such IR by the first principles quantum chemical calculation. In this paper, PAH candidates were enhanced to circumcoronene (C54H18) related molecules. Well known PAH oriented wavelength of 6.2, 7.7, 8.6, 11.3, and 12.7 micrometer were reproduced well by a void induced mono-cation (C53H18) having hydrocarbon two pentagons combined with 17 hexagons. Typical astronomical object are the red rectangle nebula and NGC6946, which is categorized as Type-B sectrum. Neutral circumcoronene show very strong IR peak at 11.1 micrometer, which is noted as Type-A spectrum observed in NGC1316 and NGC4589. Ubiquitously well observed spectrum was noted as Type-C, which could be explained by a suitable combination of Type-B and Type-A. Type-C objects are NGC7023, NGC2023 and so many. It should be noted that a dehydrogenated pure carbon mono-cation molecule (C53) show IR peaks at 6.3, 7.8, 8.5 micrometer, but no peak at 11.3 micrometer, which newly defined as Type-E. Such a strange characteristic can contribute to explain IR intensity ratio. Observed intensity ratio between peaks of 6.2, 7.7, 8.6, 11.3, and 12.7 micrometer each other were compared with above calculated IR intensities. Major intensity ratio was well reproduced by Type-B molecules. Variation of observed intensity ratio could be explained by a mixture degree between Type-B and Type-A, and also a mixture degree between Type-B and Type-E.

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N. Ota
Mon, 22 Jan 2018
35/52

Comments: 11pages, 12figures, 1 table

Engineering physics of superconducting hot-electron bolometer mixers [IMA]

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http://arxiv.org/abs/1710.09136


Superconducting hot-electron bolometers are presently the best performing mixing devices for the frequency range beyond 1.2 THz, where good quality superconductor-insulator-superconductor (SIS) devices do not exist. Their physical appearance is very simple: an antenna consisting of a normal metal, sometimes a normal metal-superconductor bilayer, connected to a thin film of a narrow, short superconductor with a high resistivity in the normal state. The device is brought into an optimal operating regime by applying a dc current and a certain amount of local- oscillator power. Despite this technological simplicity its operation has been found to be controlled by many different aspects of superconductivity, all occurring simultaneously. A core ingredient is the understanding that there are two sources of resistance in a superconductor: a charge conversion resistance occurring at an normal-metal-superconductor interface and a resistance due to time- dependent changes of the superconducting phase. The latter is responsible for the actual mixing process in a non-uniform superconducting environment set up by the bias-conditions and the geometry. The present understanding indicates that further improvement needs to be found in the use of other materials with a faster energy-relaxation rate. Meanwhile several empirical parameters have become physically meaningful indicators of the devices, which will facilitate the technological developments.

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T. Klapwijk and A. Semenov
Thu, 26 Oct 17
17/49

Comments: This is an author-processed copy of an Invited contribution to the Special Issue of the IEEE Transactions on Terahertz Science and Technology dedicated to the 28th IEEE International Symposium on Space Terahertz Technology (ISSTT2017)

Astronomical chemical evolution from graphene to polycyclic aromatic hydrocarbon reproducing observed infrared spectrum [CL]

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http://arxiv.org/abs/1703.05931


Interstellar ubiquitous infrared spectrum (IR) due to polycyclic aromatic hydrocarbon (PAH) was observed in many astronomical dust clouds. A capable astronomical chemical evolution path from graphene to PAH was studied based on the first principles calculation. Step 1 is a nucleation of nano-carbon after supernova by super-cooling at expanding helium sphere. As a typical model, graphene molecule (C )24 having coronene skeleton with seven carbon hexagons was tried.Step 2 is a proton sputtering and passivation on ejected graphene molecule. Slow speed proton with energy less than 4.3eV makes hydrogenation, Graphene molecule (C )24 was transformed to PAH (C24H12). Higher speed proton having sufficient energy larger than 18.3 eV could make a void in a molecule as like C23H12. Resulted structure was a combination of two carbon pentagons and five hexagons. Step 3 is photo-ionization of those molecules by high energy photon. Electrons are removed to make a molecule to cation. Model molecule (C23H12) became mono-cation (C23H12)+, di-cation (C23H12)2+ and so on. Typical energy difference between such cation was 6.5 and 10.8 eV. If the light source has a nature of black-body radiation, effective temperature will be 18000K ~ 24000K, which suggested that central light source star may have 4 to 7 times heavier than our sun. Finally, theoretical IR spectrum was obtained. Especially in case of (C23H12)2+, calculated emission spectrum revealed that among 13 major peaks, 11 peaks could correlate with ubiquitous observed IR one.

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N. Ota
Mon, 20 Mar 2017
35/47

Comments: 10 pages, 9 figures

Topological Origin of Geophysical Waves [CL]

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http://arxiv.org/abs/1702.07583


Symmetries and topology are central to an understanding of physics. Topology explains the precise quantization of the Hall effect and the protection of surface states in topological insulators against scattering by non-magnetic impurities or bumps. Subsequent to the discovery of the quantum spin Hall effect, states of matter with different topological properties were classified according to the discrete symmetries of the system. Recently topologically protected edge excitations have been found in artificial lattice structures that support classical waves of various types. The interplay between discrete symmetries and the topology of fluid waves has so far played no role in the study of the dynamics of oceans and atmospheres. Here we show that, as a consequence of the rotation of the Earth that breaks time reversal symmetry, equatorially trapped Kelvin and Yanai waves have a topological origin, manifesting as equatorial edge modes in the rotating shallow water model. These unidirectional edge modes are guaranteed to exist by the non-trivial global structure of the bulk Poincar\’e modes encoded through the first Chern number of value $\pm2$, in agreement with the correspondence between behavior deep in the bulk and edge excitations of a physical system. Thus the oceans and atmospheres of Earth and other rotating planets naturally share fundamental properties with topological insulators, despite the absence of an underlying lattice. As equatorially trapped Kelvin waves are an important component of El Ni\~no Southern Oscillation, and Madden-Julian Oscillation, our results demonstrate the topology plays an unexpected role in Earth’s climate system. These and other geophysical waves of topological origin are protected against static perturbations by time scale separation from other modes that inhibits scattering.

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P. Delplace, J. Marston and A. Venaille
Mon, 27 Feb 17
16/49

Comments: N/A

Stimulated Emission of Dark Matter Axion from Condensed Matter Excitations [CL]

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http://arxiv.org/abs/1612.05406


We discuss a possible principle for detecting dark matter axions in galactic halos. If axions constitute a condensate in the Milky Way, stimulated emissions of the axions from a type of excitation in condensed matter can be detectable. We provide general mechanism for the dark matter emission, and, as a concrete example, an emission of dark matter axions from magnetic vortex strings in a type II superconductor are investigated along with possible experimental signatures.

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N. Yokoi and E. Saitoh
Mon, 19 Dec 16
22/54

Comments: 20 pages, no figure

Chiral Shock Waves [CL]

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http://arxiv.org/abs/1609.07030


We study shock waves in relativistic chiral matter. We argue that the conventional Rankine- Hugoinot relations are modified due to the presence of chiral transport phenomena. We show that the entropy discontinuity in a weak shock wave is linearly proportional to the pressure discontinuity when the effect of chiral transport becomes sufficiently large. We also show that rarefaction shock waves, which do not exist in usual nonchiral fluids, can appear in chiral matter. These features are exemplified by shock propagation in dense neutrino matter in the hydrodynamic regime.

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S. Sen and N. Yamamoto
Fri, 23 Sep 16
16/50

Comments: 5 pages

Hot dense magnetized ultrarelativistic spinor matter in a slab [CL]

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http://arxiv.org/abs/1606.08241


Properties of hot dense ultrarelativistic spinor matter in a slab of finite width, placed in a transverse uniform magnetic field, are studied. The admissible set of boundary conditions is determined by the requirement that spinor matter be confined inside the slab. In thermal equilibrium, the chiral separation effect in the slab is shown to depend both on temperature and chemical potential; this is distinct from the unrealistic case of the magnetic field filling the unbounded (infinite) medium, when the effect is temperature-independent. In the realistic case of the slab, a stepwise behaviour of the axial current density at zero temperature is smoothed out as temperature increases, turning into a linear behaviour at infinitely large temperature. A choice of boundary conditions can facilitate either augmentation or attenuation of the chiral separation effect; in particular, the effect can persist even at zero chemical potential, if temperature is nonzero. Thus the boundary condition can serve as a source that is additional to the spinor matter density.

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Y. Sitenko
Tue, 28 Jun 16
32/58

Comments: 27 pages, 5 figures. arXiv admin note: text overlap with arXiv:1603.09268

High-Order Kinetic Relaxation Schemes as High-Accuracy Poisson Solvers [CL]

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http://arxiv.org/abs/1504.05869


We present a new approach to find accurate solutions to the Poisson equation, as obtained from the steady-state limit of a diffusion equation with strong source terms. For this purpose, we start from Boltzmann’s kinetic theory and investigate the influence of higher order terms on the resulting macroscopic equations. By performing an appropriate expansion of the equilibrium distribution, we provide a method to remove the unnecessary terms up to a desired order and show that it is possible to find, with high level of accuracy, the steady-state solution of the diffusion equation for sizeable Knudsen numbers. In order to test our kinetic approach, we discretise the Boltzmann equation and solve the Poisson equation, spending up to six order of magnitude less computational time for a given precision than standard lattice Boltzmann methods.

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M. Mendoza, S. Succi and H. Herrmann
Thu, 23 Apr 15
45/61

Comments: 16 pages, 6 figures

Photoluminescence of silicon-vacancy defects in nanodiamonds of different chondrites [SSA]

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http://arxiv.org/abs/1502.08031


Photoluminescence spectra show that silicon impurity is present in lattice of some nanodiamond grains (ND) of various chondrites as a silicon-vacancy (SiV) defect. The relative intensity of the SiV band in the diamond-rich separates depends on chemical composition of meteorites and on size of ND grains. The strongest signal is found for the size separates enriched in small grains; thus confirming our earlier conclusion that the SiV defects preferentially reside in the smallest (less than 2 nm) grains. The difference in relative intensities of the SiV luminescence in the diamond-rich separates of individual meteorites are due to variable conditions of thermal metamorphism of their parent bodies and/or uneven sampling of nanodiamonds populations. Annealing of separates in air eliminates surface sp2-carbon, consequently, the SiV luminescence is enhanced. Strong and well-defined luminescence and absorption of the SiV defect is a promising feature to locate cold (< 250 {\deg}C) nanodiamonds in space.

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A. Shiryaev, A. Fisenko, L. Semjonova, et. al.
Mon, 2 Mar 15
38/39

Comments: Accepted by Meteoritics and Planetary Science. 19 pages, 4 figures

A uniformly moving polarizable particle in a thermal radiation field with arbitrary spin direction [CL]

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http://arxiv.org/abs/1412.5118


We have generalized our recent results (Arm. J. Phys., 2014) relating to the dynamics, heating and radiation of a small rotating polarizable particle moving in a thermal radiation field in the case of arbitrary spin orientation. General expressions for the tangential force, heating rate and intensity of thermal and nonthermal radiation are given. It is shown that the intensity of nonthermal radiation does not depend on the linear velocity and spin direction of the particle.

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A. Kyasov and G. Dedkov
Wed, 17 Dec 14
16/67

Comments: 6 pages, 1 figure

Electrothermal Model of Kinetic Inductance Detectors [IMA]

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http://arxiv.org/abs/1411.1565


An electrothermal model of Kinetic Inductance Detectors (KIDs) is described. The non-equilibrium state of the resonator’s quasiparticle system is characterized by an effective temperature, which because of readout-power heating is higher than that of the bath. By balancing the flow of energy into the quasiparticle system, it is possible to calculate the steady-state large-signal, small-signal and noise behaviour. Resonance-curve distortion and hysteretic switching appear naturally within the framework. It is shown that an electrothermal feedback process exists, which affects all aspects of behaviour. It is also shown that generation-recombination noise can be interpreted in terms of the thermal fluctuation noise in the effective thermal conductance that links the quasiparticle and phonon systems of the resonator. Because the scheme is based on electrothermal considerations, multiple elements can be added to simulate the behaviour of complex devices, such as resonators on membranes, again taking into account readout power heating.

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C. Thomas, S. Withington and D. Goldie
Fri, 7 Nov 14
45/56

Comments: 25 pages, 3 figures

Normal Metal Hot-Electron Nanobolometer with Johnson Noise Thermometry Readout [IMA]

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http://arxiv.org/abs/1411.1118


The sensitivity of a THz hot-electron nanobolometer (nano-HEB) made from a normal metal is analyzed. Johnson Noise Thermometry (JNT) is employed as a readout technique. In contrast to its superconducting TES counterpart, the normal-metal nano-HEB can operate at any cryogenic temperature depending on the required radiation background limited Noise Equivalent Power (NEP). It does not require bias lines; 100s of nano-HEBs can be read by a single low-noise X-band amplifier via a filter bank channelizer. The modeling predicts that even with the sensitivity penalty due to the amplifier noise, an NEP ~ 10$^{-20}$ – 10$^{-19}$ W/Hz$^{1/2}$ can be expected at 50-100 mK in 10-20 nm thin titanium (Ti) normal metal HEBs with niobium (Nb) contacts. This NEP is fairly constant over a range of readout frequencies ~ 10 GHz. Although materials with weaker electron-phonon coupling (bismuth, graphene) do not improve the minimum achievable NEP, they can be considered if a larger than 10 GHz readout bandwidth is required.

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B. Karasik, C. McKitterick, T. Reck, et. al.
Thu, 6 Nov 14
14/67

Comments: 5 pages, 5 figures, presented at the 25th International Symposium on Space Terahertz Technology (Moscow, Russia, 27-30 April 2014)

Formation of Hydrocarbons from Hydrogenated Graphene in Circumstellar Clouds [CL]

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http://arxiv.org/abs/1408.4936


We describe a mechanism that explains the formation of hydrocarbons and hydrocarbyls from hydrogenated graphene/graphite; hard C-C bonds are weakened and broken by the synergistic effect of chemisorbed hydrogen and high temperature vibrations. Total energies, optimized structures, and transition states are obtained from Density Functional Theory simulations. These values have been used to determine the Boltzman probability for a thermal fluctuation to overcome the kinetic barriers, yielding the time scale for an event to occur. This mechanism can be used to rationalize the possible routes for the creation of small hydrocarbons and hydrocarbyls from etched graphene/graphite in stellar regions.

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J. Martinez, J. Martin-Gago, J. Cernicharo, et. al.
Fri, 22 Aug 14
31/49

Comments: 4.5 pages, 4 figures, 2 tables

A Strained Silicon Cold Electron Bolometer using Schottky Contacts [CL]

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http://arxiv.org/abs/1407.2113


We describe optical characterisation of a Strained Silicon Cold Electron Bolometer (CEB), operating on a $350~\mathrm{mK}$ stage, designed for absorption of millimetre-wave radiation. The silicon Cold Electron Bolometer utilises Schottky contacts between a superconductor and an n++ doped silicon island to detect changes in the temperature of the charge carriers in the silicon, due to variations in absorbed radiation. By using strained silicon as the absorber, we decrease the electron-phonon coupling in the device and increase the responsivity to incoming power. The strained silicon absorber is coupled to a planar aluminium twin-slot antenna designed to couple to $160~\mathrm{GHz}$ and that serves as the superconducting contacts. From the measured optical responsivity and spectral response, we calculate a maximum optical efficiency of $50~\%$ for radiation coupled into the device by the planar antenna and an overall noise equivalent power (NEP), referred to absorbed optical power, of $1.1 \times 10^{-16}~\mathrm{\mbox{W Hz}^{-1/2}}$ when the detector is observing a $300~\mathrm{K}$ source through a $4~\mathrm{K}$ throughput limiting aperture. Even though this optical system is not optimised we measure a system noise equivalent temperature difference (NETD) of $6~\mathrm{\mbox{mK Hz}^{-1/2}}$. We measure the noise of the device using a cross-correlation of time stream data measured simultaneously with two junction field-effect transistor (JFET) amplifiers, with a base correlated noise level of $300~\mathrm{\mbox{pV Hz}^{-1/2}}$ and find that the total noise is consistent with a combination of photon noise, current shot noise and electron-phonon thermal noise.

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T. Brien, P. Ade, P. Barry, et. al.
Tue, 5 Aug 14
8/61

Comments: Published in Applied Physics Letters, 105, pp. 043509

Precision control of thermal transport in cryogenic single-crystal silicon devices [IMA]

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http://arxiv.org/abs/1403.1326


We report on the diffusive-ballistic thermal conductance of multi-moded single-crystal silicon beams measured below 1 K. It is shown that the phonon mean-free-path $\ell$ is a strong function of the surface roughness characteristics of the beams. This effect is enhanced in diffuse beams with lengths much larger than $\ell$, even when the surface is fairly smooth, 5-10 nm rms, and the peak thermal wavelength is 0.6 $\mu$m. Resonant phonon scattering has been observed in beams with a pitted surface morphology and characteristic pit depth of 30 nm. Hence, if the surface roughness is not adequately controlled, the thermal conductance can vary significantly for diffuse beams fabricated across a wafer. In contrast, when the beam length is of order $\ell$, the conductance is dominated by ballistic transport and is effectively set by the beam area. We have demonstrated a uniformity of $\pm$8% in fractional deviation for ballistic beams, and this deviation is largely set by the thermal conductance of diffuse beams that support the micro-electro-mechanical device and electrical leads. In addition, we have found no evidence for excess specific heat in single-crystal silicon membranes. This allows for the precise control of the device heat capacity with normal metal films. We discuss the results in the context of the design and fabrication of large-format arrays of far-infrared and millimeter wavelength cryogenic detectors.

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K. Rostem, D. Chuss, F. Colazo, et. al.
Fri, 7 Mar 14
8/47