Articles de revues : « Fermi quantum gas »

1

De Marco, Luigi, Giacomo Valtolina, Kyle Matsuda, William G. Tobias, Jacob P. Covey et Jun Ye. « A degenerate Fermi gas of polar molecules ». Science 363, n^o 6429 (17 janvier 2019) : 853–56. http://dx.doi.org/10.1126/science.aau7230.

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Experimental realization of a quantum degenerate gas of molecules would provide access to a wide range of phenomena in molecular and quantum sciences. However, the very complexity that makes ultracold molecules so enticing has made reaching degeneracy an outstanding experimental challenge over the past decade. We now report the production of a degenerate Fermi gas of ultracold polar molecules of potassium-rubidium. Through coherent adiabatic association in a deeply degenerate mixture of a rubidium Bose-Einstein condensate and a potassium Fermi gas, we produce molecules at temperatures below 0.3 times the Fermi temperature. We explore the properties of this reactive gas and demonstrate how degeneracy suppresses chemical reactions, making a long-lived degenerate gas of polar molecules a reality.

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Erk а b о ev, U. I., R. G. R а khim о v, N. А. S а yid о v, J. I. Mirz а ev et U. B. Negmatov. « INFLUENCE О F А STR О NG M А GNETIC FIELD О N FERMI ENERGY О SCILL А TI О NS IN TW О -DIMENSI О N А L SEMIC О NDUCT О R M А TERI А LS ». SEMOCONDUCTOR PHYSICS AND MICROELECTRONICS 3, n^o 4 (30 août 2021) : 30–37. http://dx.doi.org/10.37681/2181-1652-019-x-2021-4-5.

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This article shows that the Fermi levels of a nanoscale semiconductor in a quantizing magnetic field are quantized. A method is proposed for calculating the Fermi energy oscillations for a two-dimensional electron gas at different magnetic fields and temperatures. An analytical expression is obtained for calculating the Fermi-Dira c distribution function at high temperatures and weak magnetic fields. With the help of the propos ed formula, the experimental results in nanoscale semiconductor structures are investigated. Using fo rmula, Fermi energy oscillations are explained for two-dimensional electron gases in quantum wells (quantum wells, mainly GaAs/GaAlAs heterostructures) with a parabolic dispersion law. Keywоrds:quаntizing mа gnetic field, temperаture, Fermi energy, n аnоscаle semicоnductоrs,twо-dimensiоnаl structures, dispersiоn.

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Dil, Emre. « Can quantum black holes be (q, p)-fermions ? » International Journal of Modern Physics A 32, n^o 15 (19 mai 2017) : 1750080. http://dx.doi.org/10.1142/s0217751x17500804.

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In this study, to investigate the very nature of quantum black holes, we try to relate three independent studies: (q, p)-deformed Fermi gas model, Verlinde’s entropic gravity proposal and Strominger’s quantum black holes obeying the deformed statistics. After summarizing Strominger’s extremal quantum black holes, we represent the thermostatistics of (q, p)-fermions to reach the deformed entropy of the (q, p)-deformed Fermi gas model. Since Strominger’s proposal claims that the quantum black holes obey deformed statistics, this motivates us to describe the statistics of quantum black holes with the (q, p)-deformed fermions. We then apply the Verlinde’s entropic gravity proposal to the entropy of the (q, p)-deformed Fermi gas model which gives the two-parameter deformed Einstein equations describing the gravitational field equations of the extremal quantum black holes obeying the deformed statistics. We finally relate the obtained results with the recent study on other modification of Einstein equations obtained from entropic quantum corrections in the literature.

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GRADO-CAFFARO, M. A., et M. GRADO-CAFFARO. « CHEMICAL POTENTIAL CALCULATION RELATIVE TO AN EXCITONIC GAS IN A NON-PARABOLIC QUANTUM DOT ». Modern Physics Letters B 20, n^o 26 (20 novembre 2006) : 1703–6. http://dx.doi.org/10.1142/s0217984906012183.

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The Fermi energy level, that is, the chemical potential associated with an excitonic gas in a semiconductor within a non-parabolic quantum dot is calculated by determining previously the corresponding Fermi velocity of excitons conceived as confined in a spherical quantum box on the basis of the energy levels of the hydrogen atom. From the Fermi energy calculation, the reduced effective mass of an electron–hole pair is found to be dependent upon the spatial exciton density. In addition, some aspects related to quantization of the Fermi energy in question and temperature dependence are discussed.

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Guan, Xiwen. « Critical phenomena in one dimension from a Bethe ansatz perspective ». International Journal of Modern Physics B 28, n^o 24 (5 août 2014) : 1430015. http://dx.doi.org/10.1142/s0217979214300151.

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This article briefly reviews recent theoretical developments in quantum critical phenomena in one-dimensional (1D) integrable quantum gases of cold atoms. We present a discussion on quantum phase transitions, universal thermodynamics, scaling functions and correlations for a few prototypical exactly solved models, such as the Lieb–Liniger Bose gas, the spin-1 Bose gas with antiferromagnetic spin-spin interaction, the two-component interacting Fermi gas as well as spin-3/2 Fermi gases. We demonstrate that their corresponding Bethe ansatz solutions provide a precise way to understand quantum many-body physics, such as quantum criticality, Luttinger liquids (LLs), the Wilson ratio, Tan's Contact, etc. These theoretical developments give rise to a physical perspective using integrability for uncovering experimentally testable phenomena in systems of interacting bosonic and fermonic ultracold atoms confined to 1D.

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Das, Samir, et Shyamal Biswas. « Particle scattering by rotating trapped quantum gases at finite temperature ». Physica Scripta 96, n^o 12 (1 décembre 2021) : 125037. http://dx.doi.org/10.1088/1402-4896/ac3d4e.

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Abstract We have analytically explored the quantum phenomena of particle scattering by rotating trapped quantum gases of electrically neutral bosons and fermions for the short-ranged Fermi-Huang interactions between the incident particle and the scatterers. We have predicted differential scattering cross-sections and their temperature and angular velocity dependencies in this regard, in particular, for an ideal Bose gas in a rotating harmonic trap, an ideal Fermi gas in a rotating harmonic trap, and a weakly interacting Bose gas in a slow rotating harmonic trap. We have theoretically probed the lattice-pattern of the vortices in a rapidly rotating strongly interacting Bose–Einstein condensate by the particle scattering method. We also have obtained de Haas-van Alphen-like oscillations in the differential scattering cross-section for an ideal ultracold Fermi gas in a rotating harmonic trap. Our predictions on the differential scattering cross-sections can be tested within the present-day experimental setups.

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Huang, Xun, Xu-Yang Hou, Yan Gong et Hao Guo. « Finite temperature behaviors of q-deformed Fermi gases ». Modern Physics Letters B 33, n^o 24 (30 août 2019) : 1950294. http://dx.doi.org/10.1142/s0217984919502944.

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During the last three decades, nonstandard statistics for indistinguishable quantum particles has attracted wide attention and research interests from many institutions. Among these new types of statistics, the [Formula: see text]-deformed Bose and Fermi statistics, originated from the study of quantum algebra, are being applied in more and more physical systems. In this paper, we construct a [Formula: see text]-deformed generalization of the BCS-Leggett theory for ultracold Fermi gases based on our previously constructed [Formula: see text]-deformed BCS theory. Some interesting features of this [Formula: see text]-deformed interacting quantum gas are obtained by numerical analysis. For example, in the ordinary Bose–Einstein Condensation regime, the gas presents a fermionic feature instead of bosonic feature if the deformation parameter is tuned suitably, which might be referred to as the [Formula: see text]-induced “Bose–Fermi” crossover. Conversely, a weak sign of the “Fermi–Bose” crossover is also found in the ordinary weak fermionic regime.

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Kokkelmans, S., M. Holland, R. Walser et M. Chiofalo. « Resonance Superfluidity in a Quantum Degenerate Fermi Gas ». Acta Physica Polonica A 101, n^o 3 (mars 2002) : 387–97. http://dx.doi.org/10.12693/aphyspola.101.387.

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Cao, C., E. Elliott, J. Joseph, H. Wu, J. Petricka, T. Schafer et J. E. Thomas. « Universal Quantum Viscosity in a Unitary Fermi Gas ». Science 331, n^o 6013 (9 décembre 2010) : 58–61. http://dx.doi.org/10.1126/science.1195219.

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Tohyama, Mitsuru. « Quantum Study of a Trapped Dipolar Fermi Gas ». Journal of the Physical Society of Japan 78, n^o 10 (15 octobre 2009) : 104003. http://dx.doi.org/10.1143/jpsj.78.104003.

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11

Sur, Saikat, et Arnab Ghosh. « Quantum Advantage of Thermal Machines with Bose and Fermi Gases ». Entropy 25, n^o 2 (17 février 2023) : 372. http://dx.doi.org/10.3390/e25020372.

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In this article, we show that a quantum gas, a collection of massive, non-interacting, indistinguishable quantum particles, can be realized as a thermodynamic machine as an artifact of energy quantization and, hence, bears no classical analog. Such a thermodynamic machine depends on the statistics of the particles, the chemical potential, and the spatial dimension of the system. Our detailed analysis demonstrates the fundamental features of quantum Stirling cycles, from the viewpoint of particle statistics and system dimensions, that helps us to realize desired quantum heat engines and refrigerators by exploiting the role of quantum statistical mechanics. In particular, a clear distinction between the behavior of a Fermi gas and a Bose gas is observed in one dimension, rather than in higher dimensions, solely due to the innate differences in their particle statistics indicating the conspicuous role of a quantum thermodynamic signature in lower dimensions.

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12

Rahman, Fahrin, Md Saidur Rahman, Rubab Ahmmed et Md Hazrat Ali. « Quantum Capacitance and Fermi Level Change in Graphene nanoribbons due to Gas Sensing ». International Journal of Applied and Structural Mechanics, n^o 31 (19 janvier 2023) : 1–9. http://dx.doi.org/10.55529/ijasm.31.1.9.

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Here we used semiempirical computations to examine the property of nanoribbon of Graphene as a gas sensor with interaction of H2O gas molecule for both pure and defective GNRs which has been generated in Atomistix Toolkit (ATK) software. Density of States GNR before and after the interaction is shown in a (DOS) diagram with gas particles was discovered to be different which has been observed in MATLAB software. It's vital to look at the quantum capacitance when examining Graphene’s electrical properties. So, this study looked at change in quantum capacitance and Fermi Level of Graphene before and after gas sensing and the results were produced with necessary equations. Using a three-electrode electrochemical setup, we are able to directly quantify Graphene's quantum capacitance as a function of gate potential. If Graphene is used in a highly sensitive capacitive circuit, the change in Fermi energy was determined from experimental data of changed Density of States (DOS). Although this research has some limitations and future scopes, we can propose that the change in Fermi Energy level can be approximately 9.5 eV with respect to the quantum capacitance of fabricated Graphene interacting with H2O which is used as a MOSFET in this work.

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Rahman, Fahrin, Md Saidur Rahman, Rubab Ahmmed Ahmmed et Md Hazrat Ali. « Quantum Capacitance and Fermi Level Change in Graphene nanoribbons due to Gas Sensing ». International Journal of Applied and Structural Mechanics, n^o 31 (19 janvier 2023) : 1–9. http://dx.doi.org/10.55529/ijasm31.1.9.

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Here we used semiempirical computations to examine the property of nanoribbon of Graphene as a gas sensor with interaction of H2O gas molecule for both pure and defective GNRs which has been generated in Atomistix Toolkit (ATK) software. Density of States GNR before and after the interaction is shown in a (DOS) diagram with gas particles was discovered to be different which has been observed in MATLAB software. It's vital to look at the quantum capacitance when examining Graphene’s electrical properties. So, this study looked at change in quantum capacitance and Fermi Level of Graphene before and after gas sensing and the results were produced with necessary equations. Using a three-electrode electrochemical setup, we are able to directly quantify Graphene's quantum capacitance as a function of gate potential. If Graphene is used in a highly sensitive capacitive circuit, the change in Fermi energy was determined from experimental data of changed Density of States (DOS). Although this research has some limitations and future scopes, we can propose that the change in Fermi Energy level can be approximately 9.5 eV with respect to the quantum capacitance of fabricated Graphene interacting with H2O which is used as a MOSFET in this work.

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Wu, Feng, Lingen Chen, Fengrui Sun, Chih Wu, Fangzhong Guo et Qing Li. « Ecological Optimization Performance of An Irreversible Quantum Otto Cycle Working with an Ideal Fermi Gas ». Open Systems & ; Information Dynamics 13, n^o 01 (mars 2006) : 55–66. http://dx.doi.org/10.1007/s11080-006-7267-4.

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The model of an irreversible Otto cycle using an ideal Fermi gas as the working fluid, which is called as the irreversible Fermi Otto cycle, is established in this paper. Based on the equation of state of an ideal Fermi gas, the ecological optimization performance of an irreversible Fermi Otto cycle is examined by taking an ecological optimization criterion as the objective, which consists of maximizing a function representing the best compromise between the exergy output and exergy loss (entropy production) of the cycle. The relationship between the ecological function E and the efficiency η is studied. Three special cases are discussed in detail. The results obtained herein may reveal the general performance characteristics of the irreversible Fermi Otto cycle.

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CHEN, LIWEI, GUOZHEN SU et JINCAN CHEN. « THE EFFECTS OF A FINITE NUMBER OF PARTICLES ON TWO TRAPPED QUANTUM GASES ». International Journal of Modern Physics B 25, n^o 32 (30 décembre 2011) : 4435–42. http://dx.doi.org/10.1142/s0217979211059243.

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The effects of a finite number of particles on the thermodynamic properties of ideal Bose and Fermi gases trapped in any-dimensional harmonic potential are investigated. The orders of relative corrections to the thermodynamic quantities due to the finite number of particles are estimated in different situations. The results obtained for the two trapped quantum gases are compared, and consequently, it is shown that the finite-particle-number effects for the condensed Bose gas (a Bose gas with Bose–Einstein Condensation (BEC) occurring in the system) are much more significant than those for the Fermi gas and normal Bose gas (a Bose gas without BEC).

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Chang, Soon-Yong, Mohit Randeria et Nandini Trivedi. « Ferromagnetism in the upper branch of the Feshbach resonance and the hard-sphere Fermi gas ». Proceedings of the National Academy of Sciences 108, n^o 1 (20 décembre 2010) : 51–54. http://dx.doi.org/10.1073/pnas.1011990108.

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We address the question of ferromagnetism in repulsive Fermi gas, a problem of fundamental interest, using quantum Monte Carlo simulations that include backflow corrections. We investigate a two-component Fermi gas on the upper branch of a Feshbach resonance and contrast it with the hard-sphere gas. We find that, in both cases, the Fermi liquid becomes unstable to ferromagnetism at a kFa smaller than the mean field result, where kF is the Fermi wavevector and a is the scattering length. Even though the total energies E(kFa) are similar in the two cases, their pair correlations and kinetic energies are completely different, reflecting the underlying potentials. We discuss the extent to which our calculations shed light on recent experiments.

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Galanakis, D., E. Khatami, K. Mikelsons, A. Macridin, J. Moreno, D. A. Browne et M. Jarrell. « Quantum criticality and incipient phase separation in the thermodynamic properties of the Hubbard model ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 369, n^o 1941 (28 avril 2011) : 1670–86. http://dx.doi.org/10.1098/rsta.2010.0228.

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Transport measurements on the cuprates suggest the presence of a quantum critical point (QCP) hiding underneath the superconducting dome near optimal hole doping. We provide numerical evidence in support of this scenario via a dynamical cluster quantum Monte Carlo study of the extended two-dimensional Hubbard model. Single-particle quantities, such as the spectral function, the quasi-particle weight and the entropy, display a crossover between two distinct ground states: a Fermi liquid at low filling and a non-Fermi liquid with a pseudo-gap at high filling. Both states are found to cross over to a marginal Fermi-liquid state at higher temperatures. For finite next-nearest-neighbour hopping t ′, we find a classical critical point at temperature T c . This classical critical point is found to be associated with a phase-separation transition between a compressible Mott gas and an incompressible Mott liquid corresponding to the Fermi liquid and the pseudo-gap state, respectively. Since the critical temperature T c extrapolates to zero as t ′ vanishes, we conclude that a QCP connects the Fermi liquid to the pseudo-gap region, and that the marginal Fermi-liquid behaviour in its vicinity is the analogue of the supercritical region in the liquid–gas transition.

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Li, Xi, Xiang Luo, Shuai Wang, Ke Xie, Xiang-Pei Liu, Hui Hu, Yu-Ao Chen, Xing-Can Yao et Jian-Wei Pan. « Second sound attenuation near quantum criticality ». Science 375, n^o 6580 (4 février 2022) : 528–33. http://dx.doi.org/10.1126/science.abi4480.

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Second sound attenuation, a distinctive dissipative hydrodynamic phenomenon in a superfluid, is crucial for understanding superfluidity and elucidating critical phenomena. Here, we report the observation of second sound attenuation in a homogeneous Fermi gas of lithium-6 atoms at unitarity by performing Bragg spectroscopy with high energy resolution in the long-wavelength limit. We successfully obtained the temperature dependence of second sound diffusivity D 2 and thermal conductivity κ. Furthermore, we observed a sudden rise—a precursor of critical divergence—in both D 2 and κ at a temperature of about 0.95 superfluid transition temperature T c . This suggests that the unitary Fermi gas has a much larger critical region than does liquid helium. Our results pave the way for determining the universal critical scaling functions near quantum criticality.

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Mitra, Debayan, Peter T. Brown, Elmer Guardado-Sanchez, Stanimir S. Kondov, Trithep Devakul, David A. Huse, Peter Schauß et Waseem S. Bakr. « Quantum gas microscopy of an attractive Fermi–Hubbard system ». Nature Physics 14, n^o 2 (23 octobre 2017) : 173–77. http://dx.doi.org/10.1038/nphys4297.

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Leboeuf, P., et A. G. Monastra. « Quantum thermodynamic fluctuations of a chaotic Fermi-gas model ». Nuclear Physics A 724, n^o 1-2 (août 2003) : 69–84. http://dx.doi.org/10.1016/s0375-9474(03)01473-8.

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Krinner, Sebastian, Martin Lebrat, Dominik Husmann, Charles Grenier, Jean-Philippe Brantut et Tilman Esslinger. « Mapping out spin and particle conductances in a quantum point contact ». Proceedings of the National Academy of Sciences 113, n^o 29 (29 juin 2016) : 8144–49. http://dx.doi.org/10.1073/pnas.1601812113.

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We study particle and spin transport in a single-mode quantum point contact, using a charge neutral, quantum degenerate Fermi gas with tunable, attractive interactions. This yields the spin and particle conductance of the point contact as a function of chemical potential or confinement. The measurements cover a regime from weak attraction, where quantized conductance is observed, to the resonantly interacting superfluid. Spin conductance exhibits a broad maximum when varying the chemical potential at moderate interactions, which signals the emergence of Cooper pairing. In contrast, the particle conductance is unexpectedly enhanced even before the gas is expected to turn into a superfluid, continuously rising from the plateau at 1/h for weak interactions to plateau-like features at nonuniversal values as high as 4/h for intermediate interactions. For strong interactions, the particle conductance plateaus disappear and the spin conductance gets suppressed, confirming the spin-insulating character of a superfluid. Our observations document the breakdown of universal conductance quantization as many-body correlations appear. The observed anomalous quantization challenges a Fermi liquid description of the normal phase, shedding new light on the nature of the strongly attractive Fermi gas.

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GRADO-CAFFARO, M. A., et M. GRADO-CAFFARO. « ON THE OPTICAL POTENTIAL OF AN ATTRACTIVE NONRELATIVISTIC DEGENERATE ELECTRON GAS INTERACTING WITH NUCLEAR MATTER ». Modern Physics Letters B 26, n^o 31 (2 novembre 2012) : 1250210. http://dx.doi.org/10.1142/s0217984912502107.

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The optical potential of an attractive nonrelativistic electron gas interacting with nuclear matter is determined on the basis of the concept of degenerate Fermi gas. In fact, the involved electrons are treated as three-dimensional quantum harmonic oscillators confined at the surface of a spherical (approximately ideal) potential well. Within this picture, the Fermi velocity is calculated as well as the spatial electron density at the surface of the potential well and the attractive force between the electron gas and the nuclear matter. In addition, considerations related to the Lippmann–Schwinger model are made.

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Aikawa, K., S. Baier, A. Frisch, M. Mark, C. Ravensbergen et F. Ferlaino. « Observation of Fermi surface deformation in a dipolar quantum gas ». Science 345, n^o 6203 (18 septembre 2014) : 1484–87. http://dx.doi.org/10.1126/science.1255259.

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Nishimura, T., et T. Maruyama. « Quantum dynamics of a dipolar Fermi gas in free expansion ». Laser Physics 20, n^o 5 (2 avril 2010) : 1177–81. http://dx.doi.org/10.1134/s1054660x10090148.

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Bettelheim, Eldad, Alexander G. Abanov et Paul B. Wiegmann. « Quantum hydrodynamics and nonlinear differential equations for degenerate Fermi gas ». Journal of Physics A : Mathematical and Theoretical 41, n^o 39 (2 septembre 2008) : 392003. http://dx.doi.org/10.1088/1751-8113/41/39/392003.

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Zhang, W. Y., L. Zhou et Y. L. Ma. « Quantum hydrodynamics and expansion of a strongly interacting Fermi gas ». EPL (Europhysics Letters) 88, n^o 4 (1 novembre 2009) : 40001. http://dx.doi.org/10.1209/0295-5075/88/40001.

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Caldas, Heron. « Superfluid-normal quantum phase transitions in an imbalanced Fermi gas ». Journal of Physics B : Atomic, Molecular and Optical Physics 53, n^o 8 (16 mars 2020) : 085301. http://dx.doi.org/10.1088/1361-6455/ab7078.

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Zhang, Ping, et Tong Liu. « Heat kernel approach for confined quantum gas ». Modern Physics Letters A 35, n^o 13 (27 février 2020) : 2050100. http://dx.doi.org/10.1142/s021773232050100x.

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In this paper, based on the heat kernel technique, we calculate equations of state and thermodynamic quantities for ideal quantum gases in confined space with external potential. Concretely, we provide expressions for equations of state and thermodynamic quantities by means of heat kernel coefficients for ideal quantum gases. Especially, using an analytic continuation treatment, we discuss the application of the heat kernel technique to Fermi gases in which the expansion diverges when the fugacity [Formula: see text]. In order to calculate the modification of heat kernel coefficients caused by external potentials, we suggest an approach for calculating the expansion of the global heat kernel of the operator [Formula: see text] based on an approximate method of the calculation of spectrum in quantum mechanics. We discuss the properties of quantum gases under the condition of weak and complete degeneration, respectively. Moreover, we give an expansion of the one-loop effective action in D-dimensional space.

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Yang, Jaw-Yen, et Yu-Hsin Shi. « A kinetic beam scheme for ideal quantum gas dynamics ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 462, n^o 2069 (14 février 2006) : 1553–72. http://dx.doi.org/10.1098/rspa.2005.1618.

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A novel kinetic beam scheme for the ideal quantum gas is presented for the computation of quantum gas dynamical flows. The quantum Boltzmann equation approach is adopted and the local thermodynamic equilibrium quantum distribution is assumed. Both Bose–Einstein and Fermi–Dirac gases are considered. Formulae for one spatial dimension is first derived and the resulting beam scheme is tested for shock tube flows. Implementation of high-order methods is also outlined. We only consider the system in the normal phase consisting of particles in excited states and both the classical limit and the nearly degenerate limit are computed. The flow structures can all be accurately captured by the present beam scheme. Formulations for multiple spatial dimensions are also included.

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Smale, Scott, Peiru He, Ben A. Olsen, Kenneth G. Jackson, Haille Sharum, Stefan Trotzky, Jamir Marino, Ana Maria Rey et Joseph H. Thywissen. « Observation of a transition between dynamical phases in a quantum degenerate Fermi gas ». Science Advances 5, n^o 8 (août 2019) : eaax1568. http://dx.doi.org/10.1126/sciadv.aax1568.

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A proposed paradigm for out-of-equilibrium quantum systems is that an analog of quantum phase transitions exists between parameter regimes of qualitatively distinct time-dependent behavior. Here, we present evidence of such a transition between dynamical phases in a cold-atom quantum simulator of the collective Heisenberg model. Our simulator encodes spin in the hyperfine states of ultracold fermionic potassium. Atoms are pinned in a network of single-particle modes, whose spatial extent emulates the long-range interactions of traditional quantum magnets. We find that below a critical interaction strength, magnetization of an initially polarized fermionic gas decays quickly, while above the transition point, the magnetization becomes long-lived because of an energy gap that protects against dephasing by the inhomogeneous axial field. Our quantum simulation reveals a nonequilibrium transition predicted to exist but not yet directly observed in quenched s-wave superconductors.

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Chebbi, Rachid. « Formulation of heat conduction and thermal conductivity of metals ». Open Physics 17, n^o 1 (8 juin 2019) : 276–80. http://dx.doi.org/10.1515/phys-2019-0028.

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Abstract The well-known low-pressure monatomic gas thermal conductivity expression is based on the Maxwell-Boltzmann velocity distribution and involves the mean particle velocity, the gas heat capacity at constant volume and the particle mean free path. The extension of the formula to a free electron Fermi gas, using the Fermi velocity along with the Sommerfeld electronic heat capacity, was demonstrated in the literature using the Boltzmann transport equation. A different formulation of heat conduction in sufficiently pure metals, yielding the same formula for the thermal conductivity, is provided in the present investigation using the free electron Fermi gas energy distribution with the thermal conductivity determined from the net heat transfer occurring due to random motions of the free electrons in the presence of temperature gradient. Potential applications of this approach include extension of the present kinetic model incorporating quantum effects to cases in which electron scattering occurs such as in nanowires and hollow nanowires.

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Amarnath, Gaini, et Trupti Ranjan Lenka. « Analytical Model Development for Unified 2D Electron Gas Sheet Charge Density of AlInN/GaN MOSHEMT ». International Journal of Electronics and Telecommunications 63, n^o 4 (27 novembre 2017) : 363–68. http://dx.doi.org/10.1515/eletel-2017-0049.

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Abstract We have developed a unified analytical model for computation of 2D electron gas sheet charge density in AlInN/GaN metal-oxide-semiconductor high electron mobility transistor device structure. This model has been developed by incorporating the variation in lowest three energy sub-bands and Fermi level energy in the quantum-well with respect to gate voltage. We noticed that the dependency of lowest sub-band energy with Fermi energy having two fields, which are the lowest sub-band energy is greater and lesser than the Fermi level energy. According to these two fields, we have developed the fermi energy and sheet charge density expressions in each field. By combining each field of the models, developed a unified 2D electron gas sheet charge density model. The Fermi level and sheet charge density are interdependent in the model development. The developed model results are compared with TCAD simulation results and obtain a good consistency between them. This model is fitted to other metal-oxide-semiconductor high electron mobility transistor devices also with modifications in related physical values.

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Levinsen, Jesper, Pietro Massignan, Georg M. Bruun et Meera M. Parish. « Strong-coupling ansatz for the one-dimensional Fermi gas in a harmonic potential ». Science Advances 1, n^o 6 (juillet 2015) : e1500197. http://dx.doi.org/10.1126/sciadv.1500197.

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A major challenge in modern physics is to accurately describe strongly interacting quantum many-body systems. One-dimensional systems provide fundamental insights because they are often amenable to exact methods. However, no exact solution is known for the experimentally relevant case of external confinement. We propose a powerful ansatz for the one-dimensional Fermi gas in a harmonic potential near the limit of infinite short-range repulsion. For the case of a single impurity in a Fermi sea, we show that our ansatz is indistinguishable from numerically exact results in both the few- and many-body limits. We furthermore derive an effective Heisenberg spin-chain model corresponding to our ansatz, valid for any spin-mixture, within which we obtain the impurity eigenstates analytically. In particular, the classical Pascal’s triangle emerges in the expression for the ground-state wave function. As well as providing an important benchmark for strongly correlated physics, our results are relevant for emerging quantum technologies, where a precise knowledge of one-dimensional quantum states is paramount.

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Patel, Parth B., Zhenjie Yan, Biswaroop Mukherjee, Richard J. Fletcher, Julian Struck et Martin W. Zwierlein. « Universal sound diffusion in a strongly interacting Fermi gas ». Science 370, n^o 6521 (3 décembre 2020) : 1222–26. http://dx.doi.org/10.1126/science.aaz5756.

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Transport of strongly interacting fermions is crucial for the properties of modern materials, nuclear fission, the merging of neutron stars, and the expansion of the early Universe. Here, we observe a universal quantum limit of diffusivity in a homogeneous, strongly interacting atomic Fermi gas by studying sound propagation and its attenuation through the coupled transport of momentum and heat. In the normal state, the sound diffusivity D monotonically decreases upon lowering the temperature, in contrast to the diverging behavior of weakly interacting Fermi liquids. Below the superfluid transition temperature, D attains a universal value set by the ratio of Planck’s constant and the particle mass. Our findings inform theories of fermion transport, with relevance for hydrodynamic flow of electrons, neutrons, and quarks.

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Schindewolf, Andreas, Roman Bause, Xing-Yan Chen, Marcel Duda, Tijs Karman, Immanuel Bloch et Xin-Yu Luo. « Evaporation of microwave-shielded polar molecules to quantum degeneracy ». Nature 607, n^o 7920 (27 juillet 2022) : 677–81. http://dx.doi.org/10.1038/s41586-022-04900-0.

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AbstractUltracold polar molecules offer strong electric dipole moments and rich internal structure, which makes them ideal building blocks to explore exotic quantum matter1–9, implement quantum information schemes10–12 and test the fundamental symmetries of nature13. Realizing their full potential requires cooling interacting molecular gases deeply into the quantum-degenerate regime. However, the intrinsically unstable collisions between molecules at short range have so far prevented direct cooling through elastic collisions to quantum degeneracy in three dimensions. Here we demonstrate evaporative cooling of a three-dimensional gas of fermionic sodium–potassium molecules to well below the Fermi temperature using microwave shielding. The molecules are protected from reaching short range with a repulsive barrier engineered by coupling rotational states with a blue-detuned circularly polarized microwave. The microwave dressing induces strong tunable dipolar interactions between the molecules, leading to high elastic collision rates that can exceed the inelastic ones by at least a factor of 460. This large elastic-to-inelastic collision ratio allows us to cool the molecular gas to 21 nanokelvin, corresponding to 0.36 times the Fermi temperature. Such cold and dense samples of polar molecules open the path to the exploration of many-body phenomena with strong dipolar interactions.

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Bach, A., et H. Zessin. « The particle structure of the quantum mechanical Bose and Fermi gas ». Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences) 52, n^o 1 (janvier 2017) : 14–29. http://dx.doi.org/10.3103/s1068362317010034.

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Cao, C., E. Elliott, H. Wu et J. E. Thomas. « Searching for perfect fluids : quantum viscosity in a universal Fermi gas ». New Journal of Physics 13, n^o 7 (21 juillet 2011) : 075007. http://dx.doi.org/10.1088/1367-2630/13/7/075007.

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DeMarco, B., S. B. Papp et D. S. Jin. « Pauli Blocking of Collisions in a Quantum Degenerate Atomic Fermi Gas ». Physical Review Letters 86, n^o 24 (11 juin 2001) : 5409–12. http://dx.doi.org/10.1103/physrevlett.86.5409.

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Sakumichi, N., et N. Kawakami. « Quantum cluster expansion study of BEC in three-component Fermi gas ». Physica C : Superconductivity and its Applications 470 (décembre 2010) : S982—S983. http://dx.doi.org/10.1016/j.physc.2009.12.005.

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Furutani, Koichiro, et Yoji Ohashi. « Strong-Coupling Effects on Quantum Transport in an Ultracold Fermi Gas ». Journal of Low Temperature Physics 201, n^o 1-2 (10 juin 2020) : 49–57. http://dx.doi.org/10.1007/s10909-020-02482-7.

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Domnenkov, A. Sh. « Markov limit for a quantum particle interacting with a Fermi gas ». Theoretical and Mathematical Physics 79, n^o 2 (mai 1989) : 524–30. http://dx.doi.org/10.1007/bf01016534.

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Bockelmann, U., Ph Roussignol, A. Filoramo, W. Heller, G. Abstreiter, K. Brunner, G. Böhm et G. Weimann. « Time Resolved Spectroscopy of Single Quantum Dots : Fermi Gas of Excitons ? » Physical Review Letters 76, n^o 19 (6 mai 1996) : 3622–25. http://dx.doi.org/10.1103/physrevlett.76.3622.

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Carlson, B. V., M. C. Nemes et A. F. R. de Toledo Piza. « Quantum collisional evolution of a one-dimensional fermi gas : Numerical solution ». Nuclear Physics A 457, n^o 2 (septembre 1986) : 261–72. http://dx.doi.org/10.1016/0375-9474(86)90376-3.

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Jacak, J. E. « Quantum contribution to luminosity of quasars ». Journal of Cosmology and Astroparticle Physics 2022, n^o 10 (1 octobre 2022) : 092. http://dx.doi.org/10.1088/1475-7516/2022/10/092.

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Abstract The accretion of galactic gas is regarded as the source of the giant luminosity of quasars. The gravitational energy converts itself into radiation close to the Schwarzschild horizon of the central supermassive black hole with efficiency of ca. 30% mass to radiation energy conversion rate. Particularities of such an extremely effective mechanism of mass to energy conversion are, however, still obscure. We propose to take into account quantum statistics properties of fermions, which could emit in close outer vicinity of the Schwarzschild zone a giant energy accumulated in the Fermi spheres of electrons and protons in degenerate quantum collective state created in this region by the gravitational compression of plasma. The release of photons is possible due to the local revoking of Pauli exclusion principle constraint induced by the rapid change of the homotopy of multiparticle trajectories beneath the innermost unstable circular orbit of the black hole, which causes the collapse of Fermi spheres of electrons and protons.

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Lin, Bihong, et Jincan Chen. « The Influence of Quantum Degeneracy on the Performance of a Fermi Brayton Engine ». Open Systems & ; Information Dynamics 11, n^o 01 (mars 2004) : 87–99. http://dx.doi.org/10.1023/b:opsy.0000024759.64343.aa.

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The influence of quantum degeneracy on the performance of a Brayton engine using an ideal Fermi gas as the working substance is investigated, based on the theory of statistical mechanics. The general expressions of the efficiency and work output of the engine cycle are derived. The maximum work output and the corresponding efficiency are calculated. The bound of the pressure ratio of the two constant-pressure processes that the Brayton engine cycle can be operated normally is determined. Some important characteristic curves of the cycle, such as the work output versus pressure ratio curves, the efficiency versus pressure ratio curves, the maximum work output ratio versus temperature of the heat reservoirs curves, and so on, are presented. Three special cases are discussed in detail. The results obtained may reveal the general performance characteristics of a Brayton engine working with an ideal Fermi gas.

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Schreiber, Katherine A., et Gábor A. Csáthy. « Competition of Pairing and Nematicity in the Two-Dimensional Electron Gas ». Annual Review of Condensed Matter Physics 11, n^o 1 (10 mars 2020) : 17–35. http://dx.doi.org/10.1146/annurev-conmatphys-031119-050550.

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Due to its extremely rich phase diagram, the two-dimensional electron gas exposed to perpendicular magnetic fields has been the subject of intense and sustained study. One particularly interesting problem in this system is that of the half-filled Landau level, where the Fermi sea of composite fermions, a fractional quantum Hall state arising from a pairing instability of the composite fermions, and the quantum Hall nematic were observed in the half-filled N = 0, N = 1, and N ≥ 2 Landau levels, respectively. Thus, different ground states developed in different half-filled Landau levels. This situation has recently changed, when evidence for both the paired fractional quantum Hall state and the quantum Hall nematic was reported in the half-filled N = 1 Landau level. Furthermore, a direct quantum phase transition between these two ordered states was found. These results highlight an intimate connection between pairing and nematicity, which is a topic of current interest in several strongly correlated systems, in a well-understood and low-disorder environment.

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El Ashram, Tarek. « Theoretical modification of Hume Rothery condition of phase stability in a good agreement with experimental data ». JOURNAL OF ADVANCES IN PHYSICS 9, n^o 3 (23 juillet 2015) : 2503–8. http://dx.doi.org/10.24297/jap.v9i3.1354.

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We presented in this paper a theoretical modification of Hume Rothery condition of phase stability in good agreement with experimental data. This modification is derived directly from the quantum conditions on the free electron Fermi gas inside the crystal. The new condition relates both the volume of Fermi sphere VF and volume of Brillouin zone VB by the valence electron concentration VEC as ;Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â for tetragonal and hexagonal systems and as; Â Â for cubic systems.

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PRZENIOSŁO, R., T. BARSZCZAK, R. KUTNER, W. GUZICKI et W. RENZ. « Monte Carlo Simulations of Lattice Gases Exhibiting Quantum Statistical Distributions ». International Journal of Modern Physics C 02, n^o 01 (mars 1991) : 450–54. http://dx.doi.org/10.1142/s0129183191000676.

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A non-interacting lattice gas with order preservation in a constant external field is studied by numerical and analytical methods. The equilibrium distribution is of the Bose-Einstein type. If additional hard-core repulsion is imposed, it becomes a distribution of Fermi-Dirac type. When relaxing the order preservation condition the classical Boltzmann distribution is recovered.

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Freik, D. M., R. O. Dzumedzey, O. B. Kostyuk et M. A. Ruvinskyy. « Quantum Size Effects in Thin Film Based on Lead Telluride ». Фізика і хімія твердого тіла 16, n^o 2 (15 juin 2015) : 284–88. http://dx.doi.org/10.15330/pcss.16.2.284-288.

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Based on the model of quantum flat rectangular and with infinitely high walls pit, the correspondences were calculated and received value of the Fermi energy and kinetic coefficients (conductivity σ, Seebeck coefficient S and thermoelectric power S2σ) for n-PbTe, by the Boltzman kinetic equation. Еhe cases with strongly degenerate and degenerate electronic gas in the films of lead telluride with n-type of conductivity are considered separately. The oscillating character of dependences of thermoelectric parameters of nanostructures based on n-PbTe for the degenerate and strongly degenerate electron gas has been theoretically proved.

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Salasnich, Luca. « Density of States for the Unitary Fermi Gas and the Schwarzschild Black Hole ». Symmetry 15, n^o 2 (27 janvier 2023) : 350. http://dx.doi.org/10.3390/sym15020350.

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The density of states of a quantum system can be calculated from its definition, but, in some cases, this approach is quite cumbersome. Alternatively, the density of states can be deduced from the microcanonical entropy or from the canonical partition function. After discussing the relationship among these procedures, we suggest a simple numerical method, which is equivalent in the thermodynamic limit to perform a Legendre transformation, to obtain the density of states from the Helmholtz free energy. We apply this method to determine the many-body density of states of the unitary Fermi gas, a very dilute system of identical fermions interacting with a divergent scattering length. The unitary Fermi gas is highly symmetric due to the absence of any internal scale except for the average distance between two particles and, for this reason, its equation of state is called universal. In the last part of the paper, by using the same thermodynamical techniques, we review some properties of the density of states of a Schwarzschild black hole, which shares the problem of finding the density of states directly from its definition with the unitary Fermi gas.

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