Journal articles: 'Supersolidity, quantum gas, quantum fluctuations'

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Norcia, Matthew A., Claudia Politi, Lauritz Klaus, Elena Poli, Maximilian Sohmen, Manfred J. Mark, Russell N. Bisset, Luis Santos, and Francesca Ferlaino. "Two-dimensional supersolidity in a dipolar quantum gas." Nature 596, no. 7872 (August 18, 2021): 357–61. http://dx.doi.org/10.1038/s41586-021-03725-7.

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Topic, O., M. Scherer, G. Gebreyesus, T. Henninger, P. Hyllus, C. Klempt, W. Ertmer, L. Santos, and J. J. Arlt. "Resonant amplification of quantum fluctuations in a spinor gas." Laser Physics 20, no. 5 (April 2, 2010): 1156–62. http://dx.doi.org/10.1134/s1054660x10090422.

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Leboeuf, P., and A. G. Monastra. "Quantum thermodynamic fluctuations of a chaotic Fermi-gas model." Nuclear Physics A 724, no. 1-2 (August 2003): 69–84. http://dx.doi.org/10.1016/s0375-9474(03)01473-8.

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KATILIUS, R., S. V. GANTSEVICH, V. D. KAGAN, and M. I. MURADOV. "FLUCTUATIONS IN NON-EQUILIBRIUM ELECTRON GAS: EFFECT OF QUANTUM STATISTICS." Fluctuation and Noise Letters 09, no. 04 (December 2010): 373–85. http://dx.doi.org/10.1142/s0219477510000290.

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Here we develop a mathematical apparatus to describe quasi-classical fluctuations in a non-equilibrium electron gas with electron-electron collisions. We substantiate the method by deriving, from general principles of quantum kinetics, an equation recently proposed by us for an equal-time electron-electron correlation function. The derivation is performed using the kinetic diagram technique. In degenerate non-equilibrium gas, the theory predicts that there exists a specific equal-time correlation between electrons. Due to the prevalence of small-angle electron-electron scattering, the equation in question takes a rather simple and treatable form (the Coulomb-type electron-electron interaction stands out against the background of all other types of interaction as one that does not generate, in the framework of quasi-classical approach, any direct exchange effects).

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Meineke, Jakob, Jean-Philippe Brantut, David Stadler, Torben Müller, Henning Moritz, and Tilman Esslinger. "Interferometric measurement of local spin fluctuations in a quantum gas." Nature Physics 8, no. 6 (April 8, 2012): 454–58. http://dx.doi.org/10.1038/nphys2280.

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Das, A., W. Florkowski, R. Ryblewski, and R. Singh. "Quantum Fluctuations of Energy in Subsystems of a Hot Relativistic Gas." Acta Physica Polonica B 52, no. 12 (2021): 1395. http://dx.doi.org/10.5506/aphyspolb.52.1395.

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MABIALA, J., A. BONASERA, H. ZHENG, A. B. MCINTOSH, Z. KOHLEY, P. CAMMARATA, K. HAGEL, et al. "CRITICAL SCALING OF TWO-COMPONENT SYSTEMS FROM QUANTUM FLUCTUATIONS." International Journal of Modern Physics E 22, no. 12 (December 2013): 1350090. http://dx.doi.org/10.1142/s0218301313500900.

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The thermodynamics of excited nuclear systems allows the exploration of a phase transition in a two-component quantum mixture. Temperatures and densities are derived from quantum fluctuations of fermions. The pressures are determined from the grand partition function of Fisher's model. Critical scaling of observables is found for the first time for fragmenting systems which differ in neutron to proton concentrations thus constraining the equation of state (EOS) of asymmetric nuclear material. The derived critical exponent, β = 0.35 ±0.01, belongs to the liquid–gas universality class. The critical compressibility factor Pc/ρcTc increases with increasing neutron concentration, which could be due to finite-size and/or Coulomb effects.

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PANG, HAI, CHENG-WEI DONG, RONG-TAO QIU, and YA-BIN ZHANG. "ANISOTROPIC PRESSURE OF A QUANTUM GAS IN CONFINED SPACE." Modern Physics Letters B 24, no. 26 (October 20, 2010): 2669–78. http://dx.doi.org/10.1142/s0217984910024973.

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In confined space, the thermodynamic potential is shape-dependent. Therefore, the pressure of ideal gases in confined space is anisotropic. We study this anisotropy in a thermodynamic manner and find that the thermodynamic pressures usually depend on the form of deformations, and hence are not equal to each other which is a natural representation of the anisotropic mechanical properties of a confined ideal gas. We also find that the boundary effects are much more significant than the statistical fluctuations under low-temperature and high-density conditions. Finally, we show that there is little difference between the boundary effects in 2D space and those in 3D space.

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Beau, Mathieu, and Adolfo del Campo. "Nonadiabatic Energy Fluctuations of Scale-Invariant Quantum Systems in a Time-Dependent Trap." Entropy 22, no. 5 (April 30, 2020): 515. http://dx.doi.org/10.3390/e22050515.

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We consider the nonadiabatic energy fluctuations of a many-body system in a time-dependent harmonic trap. In the presence of scale-invariance, the dynamics becomes self-similar and the nondiabatic energy fluctuations can be found in terms of the initial expectation values of the second moments of the Hamiltonian, square position, and squeezing operators. Nonadiabatic features are expressed in terms of the scaling factor governing the size of the atomic cloud, which can be extracted from time-of-flight images. We apply this exact relation to a number of examples: the single-particle harmonic oscillator, the one-dimensional Calogero-Sutherland model, describing bosons with inverse-square interactions that includes the non-interacting Bose gas and the Tonks-Girdardeau gas as limiting cases, and the unitary Fermi gas. We illustrate these results for various expansion protocols involving sudden quenches of the trap frequency, linear ramps and shortcuts to adiabaticity. Our results pave the way to the experimental study of nonadiabatic energy fluctuations in driven quantum fluids.

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PITAEVSKII, L. P. "TRAPPED BOSE GAS: MEAN-FIELD APPROXIMATION AND BEYOND." International Journal of Modern Physics B 13, no. 05n06 (March 10, 1999): 427–45. http://dx.doi.org/10.1142/s0217979299000333.

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The recent realization of Bose-Einstein condensation in atomic gases opens new possibilities for observation of macroscopic quantum phenomena. There are two important features of the system - weak interaction and significant spatial inhomogeneity. Because of this inhomogeneity a non-trivial "zeroth-order" theory exists, compared to the "first-order" Bogolubov theory. This theory is based on the mean-field Gross-Pitaevskii equation for the condensate ψ-function. The equation is classical in its essence but contains the ℏ constant explicitly. Phenomena such as collective modes, interference, tunneling, Josephson-like current and quantized vortex lines can be described using this equation. The study of deviations from the zeroth-order theory arising from zero-point and thermal fluctuations is also of great interest. Thermal fluctuations are described by elementary excitations which define the thermodynamic behaviour of the system and result in Landau-type damping of collective modes. Fluctuations of the phase of the condensate wave function restrict the monochromaticity of the Josephson current. Fluctuations of the numbers of quanta result in the quantum collapse-revival of the collective oscillations. This phenomenon is considered in some details. Collapse time for the JILA experimental conditions turns out to be of the order of seconds.

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Ferry, D. K., and G. Edwards. "Studies of Chaotic Transport of Electrons in Quantum Boxes." VLSI Design 6, no. 1-4 (January 1, 1998): 331–34. http://dx.doi.org/10.1155/1998/41961.

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Recent studies of transport through ballistic quantum dot resonators have revealed a complex array of behavior, including the existence of "universal" conductance fluctuations which are presumed to arise from the chaotic behavior of the underlying classical dynamics. In this paper, the results of studies on the classical ballistic transport of carriers, within a quasi-two-dimensional electron gas, through a 1.0 micron square structure in a magnetic field are presented.

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Wang, Wen-Yuan, and Wen-Lei Zhao. "Protected quantum coherence by gain and loss in a noisy quantum kicked rotor." Journal of Physics: Condensed Matter 34, no. 2 (October 29, 2021): 025403. http://dx.doi.org/10.1088/1361-648x/ac2b68.

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Abstract We study the effects of non-Hermiticity on quantum coherence via a noisy quantum kicked rotor (NQKR). The random noise comes from the fluctuations in kick amplitude at each time. The non-Hermitian driving indicates the imaginary kicking potential, representing the environment-induced atom gain and loss. In the absence of gain and loss, the random noise destroys quantum coherence manifesting dynamical localization, which leads to classical diffusion. Interestingly, in the presence of non-Hermitian kicking potential, the occurrence of dynamical localization is highly sensitive to the gain and loss, manifesting the restoration of quantum coherence. Using the inverse participation ratio arguments, we numerically obtain a phase diagram of the classical diffusion and dynamical localization on the parameter plane of noise amplitude and non-Hermitian driving strength. With the help of analysis on the corresponding quasieigenstates, we achieve insight into dynamical localization, and uncover that the origin of the localization is interference between multiple quasi-eigenstates of the quantum kicked rotor. We further propose an experimental scheme to realize the NQKR in a dissipative cold atomic gas, which paves the way for future experimental investigation of an NQKR and its anomalous non-Hermitian properties.

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Ruggiero, Paola, Pasquale Calabrese, Benjamin Doyon, and Jérôme Dubail. "Quantum generalized hydrodynamics of the Tonks–Girardeau gas: density fluctuations and entanglement entropy." Journal of Physics A: Mathematical and Theoretical 55, no. 2 (December 20, 2021): 024003. http://dx.doi.org/10.1088/1751-8121/ac3d68.

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Abstract We apply the theory of quantum generalized hydrodynamics (QGHD) introduced in (2020 Phys. Rev. Lett. 124 140603) to derive asymptotically exact results for the density fluctuations and the entanglement entropy of a one-dimensional trapped Bose gas in the Tonks–Girardeau (TG) or hard-core limit, after a trap quench from a double well to a single well. On the analytical side, the quadratic nature of the theory of QGHD is complemented with the emerging conformal invariance at the TG point to fix the universal part of those quantities. Moreover, the well-known mapping of hard-core bosons to free fermions, allows to use a generalized form of the Fisher–Hartwig conjecture to fix the non-trivial spacetime dependence of the ultraviolet cutoff in the entanglement entropy. The free nature of the TG gas also allows for more accurate results on the numerical side, where a higher number of particles as compared to the interacting case can be simulated. The agreement between analytical and numerical predictions is extremely good. For the density fluctuations, however, one has to average out large Friedel oscillations present in the numerics to recover such agreement.

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Liu, Guipeng, Ju Wu, Yanwu Lu, Guijuan Zhao, Chengyan Gu, Changbo Liu, Ling Sang, et al. "Two-dimensional electron gas mobility limited by barrier and quantum well thickness fluctuations scattering in AlxGa1−xN/GaN multi-quantum wells." Applied Physics Letters 100, no. 16 (April 16, 2012): 162102. http://dx.doi.org/10.1063/1.4704142.

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Vershik, A., and Yu Yakubovich. "Fluctuations of the Maximal Particle Energy of the Quantum Ideal Gas and Random Partitions." Communications in Mathematical Physics 261, no. 3 (October 29, 2005): 759–69. http://dx.doi.org/10.1007/s00220-005-1434-2.

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SCHELLE, ALEXEJ. "QUANTUM FLUCTUATION DYNAMICS DURING THE TRANSITION OF A MESOSCOPIC BOSONIC GAS INTO A BOSE–EINSTEIN CONDENSATE." Fluctuation and Noise Letters 11, no. 04 (December 2012): 1250027. http://dx.doi.org/10.1142/s0219477512500277.

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The condensate number distribution during the transition of a dilute, weakly interacting gas of N = 200 bosonic atoms into a Bose–Einstein condensate is modeled within number conserving master equation theory of Bose–Einstein condensation. Initial strong quantum fluctuations occuring during the exponential cycle of condensate growth reduce in a subsequent saturation stage, before the Bose gas finally relaxes towards the Gibbs–Boltzmann equilibrium.

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BIBIKOV, P. N. "GROUND-STATE FLUCTUATIONS IN RUNG-DIMERIZED SPIN LADDERS." International Journal of Modern Physics B 25, no. 09 (April 10, 2011): 1293–300. http://dx.doi.org/10.1142/s0217979211100023.

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Treating an exactly rung-dimerized spin ladder as a reference model we study perturbatively zero temperature quantum fluctuations in spin ladders with slightly destroyed rung-dimerization. Analytic expressions are obtained for the gas parameter (density of rung-triplets) and the ground-state energy per rung. At a strong diagonal frustration as well as at a rather strong antiferromagnetic rung coupling these results well agree with the previous numerical calculations.

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BRANCHINA, VINCENZO, and DARIO ZAPPALÀ. "DILUTION OF ZERO-POINT ENERGIES IN THE COSMOLOGICAL EXPANSION." Modern Physics Letters A 25, no. 27 (September 7, 2010): 2305–12. http://dx.doi.org/10.1142/s0217732310033670.

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The vacuum fluctuations of all quantum fields filling the universe are supposed to leave enormous energy and pressure contributions which are incompatible with observations. It has been recently suggested that, when the effective nature of quantum field theories is properly taken into account, vacuum fluctuations behave as a relativistic gas rather than as a cosmological constant. Accordingly, zero-point energies are tremendously diluted by the universe expansion but provide an extra contribution to radiation energy. Ongoing and future cosmological observations could offer the opportunity to scrutinize this scenario. The presence of such additional contribution to radiation energy can be tested by using primordial nucleosynthesis bounds or measured on Cosmic Background Radiation anisotropy.

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Das, A., W. Florkowski, R. Ryblewski, and R. Singh. "Quantum Baryon Number Fluctuations in Subsystems of a Hot and Dense Relativistic Gas of Fermions." Acta Physica Polonica B 53, no. 7 (2022): 1. http://dx.doi.org/10.5506/aphyspolb.53.7-a5.

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Lederer, Pascal, and Gilles Montambaux. "Quantum and thermal fluctuations of the anisotropic two-dimensional electron gas in a magnetic field." Physical Review B 37, no. 10 (April 1, 1988): 5375–86. http://dx.doi.org/10.1103/physrevb.37.5375.

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Lederer, P., and G. Montambaux. "Quantum and thermal fluctuations of the anisotropic two-dimensional electron gas in a magnetic field." Synthetic Metals 27, no. 1-2 (December 1988): A147—A152. http://dx.doi.org/10.1016/0379-6779(88)90393-1.

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Cooke, Ryan, Louise Welsh, Michele Fumagalli, and Max Pettini. "A limit on Planck-scale froth with ESPRESSO." Monthly Notices of the Royal Astronomical Society 494, no. 4 (May 6, 2020): 4884–90. http://dx.doi.org/10.1093/mnras/staa440.

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ABSTRACT Some models of quantum gravity predict that the very structure of space–time is ‘frothy’ due to quantum fluctuations. Although the effect is expected to be tiny, if these space–time fluctuations grow over a large distance, the initial state of a photon, such as its energy, is gradually washed out as the photon propagates. Thus, in these models, even the most monochromatic light source would gradually disperse in energy due to space–time fluctuations over large distances. In this paper, we use science verification observations obtained with ESPRESSO at the Very Large Telescope to place a novel bound on the growth of space–time fluctuations. To achieve this, we directly measure the width of a narrow Fe ii absorption line produced by a quiescent gas cloud at redshift $z$ ≃ 2.34, corresponding to a comoving distance of ≃5.8 Gpc. Using a heuristic model where the energy fluctuations grow as σE/E = (E/EP)α, where EP ≃ 1.22 × 1028 eV is the Planck energy, we rule out models with α ≤ 0.634, including models where the quantum fluctuations grow as a random walk process (α = 0.5). Finally, we present a new formalism where the uncertainty accrued at discrete space–time steps is drawn from a continuous distribution. We conclude, if photons take discrete steps through space–time and accumulate Planck-scale uncertainties at each step, then our ESPRESSO observations require that the step size must be at least ≳ 1013.2lP, where lP is the Planck length.

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Leturcq, R., D. L'Hote, R. Tourbot, C. J. Mellor, and M. Henini. "Resistance fluctuations in a low density 2D hole gas in GaAs." Journal de Physique IV 12, no. 9 (November 2002): 263–64. http://dx.doi.org/10.1051/jp4:20020411.

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We have measured the resistance fluctuations in 2D hole gases in GaAs quantum wells around the 2D “metal"-insulator transition (MIT) at temperatures between 35 and 700 mK. The magnitude of the noise spectrum has a l/$^\alpha ( \alpha = 1)$ frequency dependence and increases strongly as the density is lowered. There is a qualitative change in the temperature dependence at a density pg, higher than the 2D MIT critical density pc. Moreover, the noise magnitude shows a scaling behaviour as a function of the resistance, which can be attributed to a percolation transition, as suggested by theories which explain the resistivity vs. temperature dependence near the 2D MIT.

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Schwengelbeck, Uwe, Enrique Conejero Jarque, Luis Plaja, and Luis Roso. "Quantum description of charge fluctuations in electron gas and plasma wave response to intense laser interaction." Journal of Physics B: Atomic, Molecular and Optical Physics 31, no. 23 (December 14, 1998): 5215–20. http://dx.doi.org/10.1088/0953-4075/31/23/018.

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Qi, Wei, Liang-Wei Dong, and Hai-Feng Li. "Effects of Quantum Fluctuations on ${\mathscr{P}}{\mathscr{T}}$-Symmetric Solitons of a Trapped Bose Gas." Communications in Theoretical Physics 71, no. 7 (July 2019): 773. http://dx.doi.org/10.1088/0253-6102/71/7/773.

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CASTELLANOS, E., and C. LÄMMERZAHL. "IDEAL-MODIFIED BOSONIC GAS TRAPPED IN AN ARBITRARY THREE-DIMENSIONAL POWER-LAW POTENTIAL." Modern Physics Letters A 27, no. 31 (October 4, 2012): 1250181. http://dx.doi.org/10.1142/s0217732312501817.

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We analyze the effects caused by an anomalous single-particle dispersion relation suggested in several quantum-gravity models, upon the thermodynamics of a Bose–Einstein condensate trapped in a generic three-dimensional power-law potential. We prove that the shift in the condensation temperature, caused by a deformed dispersion relation, described as a non-trivial function of the number of particles and the shape associated to the corresponding trap, could provide bounds for the parameters associated to such deformation. In addition, we calculate the fluctuations in the number of particles as a criterium of thermodynamic stability for these systems. We show that the apparent instability caused by the anomalous fluctuations in the thermodynamic limit can be suppressed considering the lowest energy associated to the system in question.

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Mukim, S., J. O’Brien, M. Abarashi, M. S. Ferreira, and C. G. Rocha. "Decoding the conductance of disordered nanostructures: a quantum inverse problem." Journal of Physics: Condensed Matter 34, no. 8 (December 3, 2021): 085901. http://dx.doi.org/10.1088/1361-648x/ac3a85.

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Abstract Obtaining conductance spectra for a concentration of disordered impurities distributed over a nanoscale device with sensing capabilities is a well-defined problem. However, to do this inversely, i.e., extracting information about the scatters from the conductance spectrum alone, is not an easy task. In the presence of impurities, even advanced techniques of inversion can become particularly challenging. This article extends the applicability of a methodology we proposed capable of extracting composition information about a nanoscale sensing device using the conductance spectrum. The inversion tool decodes the conductance spectrum to yield the concentration and nature of the disorders responsible for conductance fluctuations in the spectra. We present the method for simple one-dimensional systems like an electron gas with randomly distributed delta functions and a linear chain of atoms. We prove the generality and robustness of the method using materials with complex electronic structures like hexagonal boron nitride, graphene nanoribbons, and carbon nanotubes. We also go on to probe distribution of disorders on the sublattice structure of the materials using the proposed inversion tool.

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Adhikari, Kiran, Sayantan Choudhury, Hardey N. Pandya, and Rohan Srivastava. "Primordial Gravitational Wave Circuit Complexity." Symmetry 15, no. 3 (March 6, 2023): 664. http://dx.doi.org/10.3390/sym15030664.

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In this article, we investigate the various physical implications of quantum circuit complexity using the squeezed state formalism of Primordial Gravitational Waves (PGW). Recently, quantum information-theoretic concepts, such as entanglement entropy and complexity, have played a pivotal role in understanding the dynamics of quantum systems, even in diverse fields such as high-energy physics and cosmology. This paper is devoted to studying the quantum circuit complexity of PGW for various cosmological models, such as de Sitter, inflation, radiation, reheating, matter, bouncing, cyclic and black hole gas models, etc. We compute complexity measures using both Covariance and Nielsen’s wave function method for three different choices of quantum initial vacua: Motta-Allen, α and Bunch–Davies. Besides computing circuit complexity, we also compute the Von Neumann entanglement entropy. By making the comparison between complexity and entanglement entropy, we are able to probe various features regarding the dynamics of evolution for different cosmological models. Because entanglement entropy is independent of the squeezing angle, we are able to understand more details of the system using Nielsen’s measure of complexity, which is dependent on both squeezing parameter and angle. This implies that quantum complexity could indeed be a useful probe to study quantum features on a cosmological scale. Quantum complexity is also becoming a powerful technique to understand the chaotic behaviour and random fluctuations of quantum fields. Using the growth of complexity, we are able to compute the quantum Lyapunov exponent for various cosmological models and comment on its chaotic nature.

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Rodriguez, J. P., and Pascal Lederer. "De Haas-Van Alphen and Shubnikov-De Haas Oscillations in Strongly Correlated Electron Gas." International Journal of Modern Physics B 06, no. 05n06 (March 1992): 497–507. http://dx.doi.org/10.1142/s0217979292000281.

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We investigate the de Haas van Alphen (dHvA) and Shubnikov-de Haas (SdH) oscillations in a 2D strongly correlated electron system. The normal state is described by the fluxless phase (uniform RVB) of the t−J model. In the quantum limit, we find that conventional 2D dHvA sawtooth behavior is unattainable: in the limit near half-filling, where the magnetic energy dominates, one has square wave dHvA behavior with reduced amplitude; far from half-filling one finds a mixed square wave-sawtooth regime. The dHvA oscillation frequency is unchanged in all regimes, and it corresponds to Luttinger’s Fermi surface. A conventional SdH effect exists in the above mentioned conventional regime, whereas it is absent in the square-wave dHvA regime. Lastly, it is shown that the linear-in-T contribution to the resistivity arising from chiral fluctuations in the fluxless phase dissappears in the presence of magnetic field in the quantum limit. We therefore predict that this strongly correlated metal shows a large negative magneto-resistance.

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Bonnemain, Thibault, Benjamin Doyon, and Gennady El. "Generalized hydrodynamics of the KdV soliton gas." Journal of Physics A: Mathematical and Theoretical 55, no. 37 (August 19, 2022): 374004. http://dx.doi.org/10.1088/1751-8121/ac8253.

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Abstract We establish the explicit correspondence between the theory of soliton gases in classical integrable dispersive hydrodynamics, and generalized hydrodynamics (GHD), the hydrodynamic theory for many-body quantum and classical integrable systems. This is done by constructing the GHD description of the soliton gas for the Korteweg–de Vries equation. We further predict the exact form of the free energy density and flux, and of the static correlation matrices of conserved charges and currents, for the soliton gas. For this purpose, we identify the solitons’ statistics with that of classical particles, and confirm the resulting GHD static correlation matrices by numerical simulations of the soliton gas. Finally, we express conjectured dynamical correlation functions for the soliton gas by simply borrowing the GHD results. In principle, other conjectures are also immediately available, such as diffusion and large-deviation functions for fluctuations of soliton transport.

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Gavrilik, Alexandre M., and Andriy V. Nazarenko. "Bose–Einstein Condensate Dark Matter That Involves Composites." Universe 8, no. 3 (March 17, 2022): 187. http://dx.doi.org/10.3390/universe8030187.

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Improving the Bose–Einstein condensate model of dark matter through the repulsive three-particle interaction to better reproduce observables such as rotation curves reveals both different thermodynamic phases and few-particle correlations. Using the numerically found solutions of the Gross–Pitaevskii equation for averaging the products of local densities and for calculating thermodynamic functions at zero temperature, it is shown that the few-particle correlations imply a first-order phase transition and are reduced to the product of single-particle averages with a simultaneous increase in pressure, density, and quantum fluctuations. Under given conditions, dark matter exhibits the properties of an ideal gas with an effective temperature determined by quantum fluctuations. Characteristics of oscillations between bound and unbound states of three particles are estimated within a simple random walk approach to qualitatively model the instability of particle complexes. On the other hand, the density-dependent conditions for the formation of composites are analyzed using chemical kinetics without specifying the bonds formed. The obtained results can be extended to the models of multicomponent dark matter consisting of composites formed by particles with a large scattering length.

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Khan, Ayan, Saurabh Basu, and B. Tanatar. "Investigating dirty crossover through fidelity susceptibility and density of states." International Journal of Modern Physics B 28, no. 14 (April 25, 2014): 1450083. http://dx.doi.org/10.1142/s0217979214500830.

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We investigate the BCS–BEC crossover in an ultracold atomic gas in the presence of disorder. The disorder is incorporated in the mean-field formalism through Gaussian fluctuations. We observe evolution to an asymmetric line-shape of fidelity susceptibility (FS) as a function of interaction coupling with increasing disorder strength which may point to an impending quantum phase transition (QPT). The asymmetric line-shape is further analyzed using the statistical tools of skewness and kurtosis. We extend our analysis to density of states (DOS) for a better understanding of the crossover in the disordered environment.

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Choi, Hyungkook, Minsoo Kim, Ji-Yun Moon, Jae-Hyun Lee, and Seok-Kyun Son. "One-Dimensional Poisson Calculation for Electrically Controlled Band Bending in GaAs/AlGaAs Heterostructure." Journal of Nanoscience and Nanotechnology 20, no. 7 (July 1, 2020): 4428–31. http://dx.doi.org/10.1166/jnn.2020.17559.

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Here, we describe the band-bending situation for introducing electrons in an undoped GaAs and AlGaAs quantum well. Our calculation has shown that an externally applied electric field can modulate two-dimensional electron gas (2DEG) without standard modulation doping. The topic of electrically modulated 2DEG has only background impurities, no intentional dopants, so scattering or dephasing by background potential fluctuations should be much reduced. Using our calculation, it is straightforward to confine carriers (in the range of 1010~1011 cm−2), when the external electric field is more than threshold voltage, 4 V to the surface metal gate.

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Vovchenko, Volodymyr, Paolo Alba, Mark I. Gorenstein, and Horst Stoecker. "van der Waals Interactions and Hadron Resonance Gas: Role of resonance widths modeling on conserved charges fluctuations." EPJ Web of Conferences 171 (2018): 14006. http://dx.doi.org/10.1051/epjconf/201817114006.

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The quantum van der Waals (QvdW) extension of the ideal hadron resonance gas (HRG) model which includes the attractive and repulsive interactions between baryons – the QvdW-HRG model – is applied to study the behavior of the baryon number related susceptibilities in the crossover temperature region. Inclusion of the QvdW interactions leads to a qualitatively different behavior of susceptibilities, in many cases resembling lattice QCD simulations. It is shown that for some observables, in particular for χBQ11/χB2, effects of the QvdW interactions essentially cancel out. It is found that the inclusion of the finite resonance widths leads to an improved description of χB2, but it also leads to a worse description of χBQ11/χB2, as compared to the lattice data. On the other hand, inclusion of the extra, unconfirmed baryons into the hadron list leads to a simultaneous improvement in the description of both observables.

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Bellwied, Rene. "Sequential Strangeness Freeze-out." EPJ Web of Conferences 171 (2018): 02006. http://dx.doi.org/10.1051/epjconf/201817102006.

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I will describe the latest results from lattice QCD pertaining to a potential flavour hierarchy in the hadronic freeze-out from the QCD crossover region. I will compare these results to a variety of improved hadronic resonance gas calculations and to experimental data of fluctuations of net-charge, net-proton and net-kaon multiplicity distributions, which serve as a proxy for the susceptibilities of conserved quantum numbers on the lattice. I will conclude that there is intriguing evidence for a flavour dependent freezeout, and I will suggest expansions to the experimental program at RHIC and the LHC that could potentially demonstrate the impact of a flavour separation during hadronization.

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Tajima, Hiroyuki, Junichi Takahashi, Simeon Mistakidis, Eiji Nakano, and Kei Iida. "Polaron Problems in Ultracold Atoms: Role of a Fermi Sea across Different Spatial Dimensions and Quantum Fluctuations of a Bose Medium." Atoms 9, no. 1 (March 9, 2021): 18. http://dx.doi.org/10.3390/atoms9010018.

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The notion of a polaron, originally introduced in the context of electrons in ionic lattices, helps us to understand how a quantum impurity behaves when being immersed in and interacting with a many-body background. We discuss the impact of the impurities on the medium particles by considering feedback effects from polarons that can be realized in ultracold quantum gas experiments. In particular, we exemplify the modifications of the medium in the presence of either Fermi or Bose polarons. Regarding Fermi polarons we present a corresponding many-body diagrammatic approach operating at finite temperatures and discuss how mediated two- and three-body interactions are implemented within this framework. Utilizing this approach, we analyze the behavior of the spectral function of Fermi polarons at finite temperature by varying impurity-medium interactions as well as spatial dimensions from three to one. Interestingly, we reveal that the spectral function of the medium atoms could be a useful quantity for analyzing the transition/crossover from attractive polarons to molecules in three-dimensions. As for the Bose polaron, we showcase the depletion of the background Bose-Einstein condensate in the vicinity of the impurity atom. Such spatial modulations would be important for future investigations regarding the quantification of interpolaron correlations in Bose polaron problems.

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37

ARDARAVICIUS, L., J. LIBERIS, A. MATULIONIS, and M. RAMONAS. "ESTIMATION OF ELECTRON ENERGY RELAXATION TIME IN 2DEG CHANNELS FROM TRANSVERSE AND LONGITUDINAL NOISE." Fluctuation and Noise Letters 02, no. 01 (March 2002): L53—L63. http://dx.doi.org/10.1142/s0219477502000592.

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Microwave noise is investigated in heterostructures subjected to an electric field applied parallel to the interfaces. The longitudinal and transverse noise temperatures are measured and simulated in the plane of electron confinement in the directions perpendicular and parallel to the electric field. Monte Carlo simulation is performed for a subcritically doped InAlAs/InGaAs/InAlAs heterostructure containing a two-dimensional electron gas in a single channel. The simulated longitudinal noise temperature is found to be nearly the same as the transverse one in the field range where the interwell transfer of hot electrons is not important. The longitudinal noise temperature exceeds the transverse one considerably in a supercritically doped InAlAs/InGaAs/InAlAs/InP heterostructure containing three separate quantum-well channels, each accommodating a two-dimensional electron gas at equilibrium. The observed strong planar anisotropy is ascribed to the channel occupancy fluctuations caused by the interwell transfer of equilibrium electrons. A possibility to estimate energy relaxation time from the transverse and the longitudinal microwave noise measurements is discussed.

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Sasaki, Chihiro, David Blaschke, Pok Man Lo, Michał Marczenko, Kenji Morita, and Krzysztof Redlich. "Parity Doubling in QCD Thermodynamics." Proceedings 13, no. 1 (June 24, 2019): 7. http://dx.doi.org/10.3390/proceedings2019013007.

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Motivated by the recent lattice study by FASTSUM collaboration, effective masses of the baryon parity-doublers are shown for various pion masses. A general trend of the nucleon and delta parity-doublers is consistent with the lattice Quantum Chromodynamics (QCD) observation, whereas the hyperon masses exhibit a qualitatively different behavior, traced back to the lattice set-up with the heavy pion comparable to the kaon. As an application to hot QCD, we demonstrate the fluctuations and correlations involving baryon number in hot hadronic matter with modified masses of negative-parity baryons, in the context of the hadron resonance gas. Confronting the baryon number susceptibility, baryon–charge and baryon–strangeness correlations as well as their ratios with the lattice QCD data for the physical pion mass, we find that the strong downward mass shift in the hyperons can accidentally reproduce some correlation ratios, however it also tends to overshoot the individual fluctuations and correlations of lattice simulations. Another application of nucleon parity doubling is the physics of neutron stars. Under beta equilibrium and charge neutrality, hadronic matter with unbroken chiral symmetry can be favored in the core of the neutron stars.

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Chamberlin, Ralph V., Michael R. Clark, Vladimiro Mujica, and George H. Wolf. "Multiscale Thermodynamics: Energy, Entropy, and Symmetry from Atoms to Bulk Behavior." Symmetry 13, no. 4 (April 19, 2021): 721. http://dx.doi.org/10.3390/sym13040721.

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Here, we investigate how the local properties of particles in a thermal bath may influence the thermodynamics of the bath, and consequently alter the statistical mechanics of subsystems that comprise the bath. We are guided by the theory of small-system thermodynamics, which is based on two primary postulates: that small systems can be treated self-consistently by coupling them to an ensemble of similarly small systems, and that a large ensemble of small systems forms its own thermodynamic bath. We adapt this “nanothermodynamics” to investigate how a large system may subdivide into an ensemble of smaller subsystems, causing internal heterogeneity across multiple size scales. For the semi-classical ideal gas, maximum entropy favors subdividing a large system of “atoms” into an ensemble of “regions” of variable size. The mechanism of region formation could come from quantum exchange symmetry that makes atoms in each region indistinguishable, while decoherence between regions allows atoms in separate regions to be distinguishable by their distinct locations. Combining regions reduces the total entropy, as expected when distinguishable particles become indistinguishable, and as required by a theorem in quantum mechanics for sub-additive entropy. Combining large volumes of small regions gives the usual entropy of mixing for a semi-classical ideal gas, resolving Gibbs paradox without invoking quantum symmetry for particles that may be meters apart. Other models presented here are based on Ising-like spins, which are solved analytically in one dimension. Focusing on the bonds between the spins, we find similarity in the equilibrium properties of a two-state model in the nanocanonical ensemble and a three-state model in the canonical ensemble. Thus, emergent phenomena may alter the thermal behavior of microscopic models, and the correct ensemble is necessary for fully-accurate predictions. Another result using Ising-like spins involves simulations that include a nonlinear correction to Boltzmann’s factor, which mimics the statistics of indistinguishable states by imitating the dynamics of spin exchange on intermediate lengths. These simulations exhibit 1/f-like noise at low frequencies (f), and white noise at higher f, similar to the equilibrium thermal fluctuations found in many materials.

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40

Sindona, Antonello, Michele Pisarra, Mario Gravina, Cristian Vacacela Gomez, Pierfrancesco Riccardi, Giovanni Falcone, and Francesco Plastina. "Statistics of work and orthogonality catastrophe in discrete level systems: an application to fullerene molecules and ultra-cold trapped Fermi gases." Beilstein Journal of Nanotechnology 6 (March 18, 2015): 755–66. http://dx.doi.org/10.3762/bjnano.6.78.

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The sudden introduction of a local impurity in a Fermi sea leads to an anomalous disturbance of its quantum state that represents a local quench, leaving the system out of equilibrium and giving rise to the Anderson orthogonality catastrophe. The statistics of the work done describe the energy fluctuations produced by the quench, providing an accurate and detailed insight into the fundamental physics of the process. We present here a numerical approach to the non-equilibrium work distribution, supported by applications to phenomena occurring at very diverse energy ranges. One of them is the valence electron shake-up induced by photo-ionization of a core state in a fullerene molecule. The other is the response of an ultra-cold gas of trapped fermions to an embedded two-level atom excited by a fast pulse. Working at low thermal energies, we detect the primary role played by many-particle states of the perturbed system with one or two excited fermions. We validate our approach through the comparison with some photoemission data on fullerene films and previous analytical calculations on harmonically trapped Fermi gases.

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Fatahian, E., Ebrahim Hosseini, and H. Fatahian. "A review on recent research studies on vibration analysis of fluid-conveying nanotubes." International Journal of Engineering Technology and Sciences 7, no. 2 (September 23, 2020): 42–54. http://dx.doi.org/10.15282/ijets.7.2.2020.1004.

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Nanotube (such as carbon and boron nitride nanotubes) is a key component of modern technology applications of nanostructures due to their unique mechanical, electrical, and physical characteristics such as high elasticity modulus, suitable heat transfer, and electrical conductivity. Carbon and boron nitride nanotubes are among the promising choices in nano-fluidic, gas storage, and drug delivery systems due to their hollow cylindrical shape and appropriate chemical, mechanical, and physical properties. Thermal vibration assessment should be conducted on fluid-conveying carbon nanotubes since the effect of thermal fluctuations on the mechanical characteristics of nanostructure are significant. Previous studies have revealed that when thermal vibration is taken into account, quantum effects can become extremely important in nanoscale electronics and structures. Hence, the present review focuses mostly on previous work on fluid-conveying nanotubes and the dynamical characteristics of size-dependent vibration and non-local strain gradient theory of fluid-conveying nanotubes. Furthermore, a special effort is made to address recent and rare investigations on the vibration of fluid-conveying nanotubes in thermal environment, as well as thermal vibration concerns of carbon nanotubes.

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CASAHORRÁN, J. "THE EUCLIDEAN PROPAGATOR IN A MODEL WITH TWO NON-EQUIVALENT INSTANTONS." Modern Physics Letters A 17, no. 18 (June 14, 2002): 1165–74. http://dx.doi.org/10.1142/s0217732302007211.

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We consider in detail how the quantum-mechanical tunneling phenomenon occurs in a well-behaved octic potential. Our main tool will be the Euclidean propagator just evaluated between two minima of the potential at issue. For such a purpose we resort to the standard semiclassical approximation which takes into account the fluctuations over the instantons, i.e. the finite-action solutions of the Euclidean equation of motion. With respect to the one-instanton approach, the functional determinant associated with the so-called stability equation is analyzed in terms of the asymptotic behavior of the zero-mode. The conventional ratio of determinants takes as reference the harmonic oscillator whose frequency is the average of the two different frequencies derived from the minima of the potential involved in the computation. The second instanton of the model is studied in a similar way. The physical effects of the multi-instanton configurations are included in this context by means of the alternate dilute-gas approximation where the two instantons participate to give the final expression of the propagator.

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Reggiani, Lino, and Eleonora Alfinito. "Fluctuation Dissipation Theorem and Electrical Noise Revisited." Fluctuation and Noise Letters 18, no. 01 (January 9, 2019): 1930001. http://dx.doi.org/10.1142/s0219477519300015.

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The fluctuation dissipation theorem (FDT) is the basis for a microscopic description of the interaction between electromagnetic radiation and matter. By assuming the electromagnetic radiation in thermal equilibrium and the interaction in the linear-response regime, the theorem interrelates the macroscopic spontaneous fluctuations of an observable with the kinetic coefficients that are responsible for energy dissipation in the linear response to an applied perturbation. In the quantum form provided by Callen and Welton in their pioneering paper of 1951 for the case of conductors [H. B. Callen and T. A. Welton, Irreversibility and generalized noise, Phys. Rev. 83 (1951) 34], electrical noise in terms of the spectral density of voltage fluctuations, [Formula: see text], detected at the terminals of a conductor was related to the real part of its impedance, [Formula: see text], by the simple relation [Formula: see text] where [Formula: see text] is the Boltzmann constant, [Formula: see text] is the absolute temperature, [Formula: see text] is the reduced Planck constant and [Formula: see text] is the angular frequency. The drawbacks of this relation concern with: (i) the appearance of a zero-point contribution which implies a divergence of the spectrum at increasing frequencies; (ii) the lack of detailing the appropriate equivalent-circuit of the impedance, (iii) the neglect of the Casimir effect associated with the quantum interaction between zero-point energy and boundaries of the considered physical system; (iv) the lack of identification of the microscopic noise sources beyond the temperature model. These drawbacks do not allow to validate the relation with experiments, apart from the limiting conditions when [Formula: see text]. By revisiting the FDT within a brief historical survey of its formulation, since the announcement of Stefan–Boltzmann law dated in the period 1879–1884, we shed new light on the existing drawbacks by providing further properties of the theorem with particular attention to problems related with the electrical noise of a two-terminals sample under equilibrium conditions. Accordingly, among others, we will discuss the duality and reciprocity properties of the theorem, the role played by different statistical ensembles, its applications to the ballistic transport-regime, to the case of vacuum and to the case of a photon gas.

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Rakocevic, Miroslava, Eunice R. Batista, Ricardo A. A. Pazianotto, Maria B. S. Scholz, Guilherme A. R. Souza, Eliemar Campostrini, and José C. Ramalho. "Leaf gas exchange and bean quality fluctuations over the whole canopy vertical profile of Arabic coffee cultivated under elevated CO2." Functional Plant Biology 48, no. 5 (2021): 469. http://dx.doi.org/10.1071/fp20298.

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Leaves in different positions respond differently to dynamic ﬂuctuations in light availability, temperature and to multiple environmental stresses. The current hypothesis states that elevated atmospheric CO2 (e[CO2]) can compensate for the negative effects of water scarcity regarding leaf gas exchanges and coffee bean quality traits over the canopy vertical profile, in interactions with light and temperature microclimate during the two final stages of berry development. Responses of Coffea arabica L. were observed in the 5th year of a free air CO2 enrichment experiment (FACE) under water-limited rainfed conditions. The light dependent leaf photosynthesis curves (A/PAR) were modelled for leaves sampled from vertical profile divided into four 50-cm thick layers. e[CO2] significantly increased gross photosynthesis (AmaxGross), the apparent quantum yield efficiency, light compensation point, light saturation point (LSP) and dark respiration rate (Rd). As a specific stage response, considering berry ripening, all parameters calculated from A/PAR were insensitive to leaf position over the vertical profile. Lack of a progressive increase in AmaxGross and LSP was observed over the whole canopy profile in both stages, especially in the two lowest layers, indicating leaf plasticity to light. Negative correlation of Rd to leaf temperature (TL) was observed under e[CO2] in both stages. Under e[CO2], stomatal conductance was also negatively correlated with TL, reducing leaf transpiration and Rd even with increasing TL. This indicated coffee leaf acclimation to elevated temperatures under e[CO2] and water restriction. The e[CO2] attenuation occurred under water restriction, especially in A and water use efficiency, in both stages, with the exception of the lowest two layers. Under e[CO2], coffee produced berries in moderate- and high light level layers, with homogeneous distribution among them, contrasted to the heterogeneous distribution under actual CO2. e[CO2] led to increased caffeine content in the highest layer, with reduction of chlorogenic acid and lipids under moderate light and to raised levels of sugar in the shaded low layer. The ability of coffee to respond to e[CO2] under limited soil water was expressed through the integrated individual leaf capacities to use the available light and water, resulting in final plant investments in new reproductive structures in moderate and high light level layers.

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45

Kumar, Divyanshu, and Cheng-Shane Chu. "A Ratiometric Optical Dual Sensor for the Simultaneous Detection of Oxygen and Carbon Dioxide." Sensors 21, no. 12 (June 12, 2021): 4057. http://dx.doi.org/10.3390/s21124057.

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Simultaneous detection of carbon dioxide (CO2) and oxygen (O2) has attracted considerable interest since CO2 and O2 play key roles in various industrial and domestic applications. In this study, a new approach based on a fluorescence ratiometric referencing method was reported to develop an optical dual sensor where platinum (II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) complex used as the O2-sensitive dye, CdSe/ZnS quantum dots (QDs) combined with phenol red used as the CO2-sensitive dye, and CdSe/ZnS QDs used as the reference dye for the simultaneous detection of O2 and CO2. All the dyes were immobilized in a gas-permeable matrix poly (isobutyl methacrylate) (PolyIBM) and subjected to excitation using a 380 nm LED. The as-obtained distinct fluorescence spectral intensities were alternately exposed to analyte gases to observe changes in the fluorescence intensity. In the presence of O2, the fluorescence intensity of the Pt (II) complex was considerably quenched, while in the presence of CO2, the fluorescence intensity of QDs was increased. The corresponding ratiometric sensitivities of the optical dual sensor for O2 and CO2 were approximately 13 and 144, respectively. In addition, the response and recovery for O2 and CO2 were calculated to be 10 s/35 s and 20 s/60 s, respectively. Thus, a ratiometric optical dual gas sensor for the simultaneous detection of O2 and CO2 was successfully developed. Effects of spurious fluctuations in the intensity of external and excitation sources were suppressed by the ratiometric sensing approach.

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46

Nasser Tawfik, Abdel, and Hend Magdy. "Hadronic equation of state and speed of sound in thermal and dense medium." International Journal of Modern Physics A 29, no. 27 (October 28, 2014): 1450152. http://dx.doi.org/10.1142/s0217751x14501528.

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The equation of state p(ϵ) and speed of sound squared [Formula: see text] are studied in grand canonical ensemble of all hadron resonances having masses ≤2 GeV . This large ensemble is divided into strange and non-strange hadron resonances and furthermore to pionic, bosonic and fermionic sectors. It is found that the pions represent the main contributors to [Formula: see text] and other thermodynamic quantities including the equation of state p(ϵ) at low temperatures. At high temperatures, the main contributions are added in by the massive hadron resonances. The speed of sound squared can be calculated from the derivative of pressure with respect to the energy density, ∂p/∂ϵ, or from the entropy-specific heat ratio, s/cv. It is concluded that the physics of these two expressions is not necessarily identical. They are distinguishable below and above the critical temperature Tc. This behavior is observed at vanishing and finite chemical potential. At high temperatures, both expressions get very close to each other and both of them approach the asymptotic value, 1/3. In the hadron resonance gas (HRG) results, which are only valid below Tc, the difference decreases with increasing the temperature and almost vanishes near Tc. It is concluded that the HRG model can very well reproduce the results of the lattice quantum chromodynamics (QCD) of ∂p/∂ϵ and s/cv, especially at finite chemical potential. In light of this, energy fluctuations and other collective phenomena associated with the specific heat might be present in the HRG model. At fixed temperatures, it is found that [Formula: see text] is not sensitive to the chemical potential.

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Negretti, Antonio, Carsten Henkel, and Klaus Mølmer. "Quantum fluctuations in the image of a Bose gas." Physical Review A 78, no. 2 (August 25, 2008). http://dx.doi.org/10.1103/physreva.78.023630.

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Sanner, Christian, Edward J. Su, Aviv Keshet, Ralf Gommers, Yong-il Shin, Wujie Huang, and Wolfgang Ketterle. "Suppression of Density Fluctuations in a Quantum Degenerate Fermi Gas." Physical Review Letters 105, no. 4 (July 19, 2010). http://dx.doi.org/10.1103/physrevlett.105.040402.

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Singh, Rajeev. "A compact formula for the quantum fluctuations of energy." Suplemento de la Revista Mexicana de Física 3, no. 3 (May 18, 2022). http://dx.doi.org/10.31349/suplrevmexfis.3.0308115.

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A formula to calculate the quantum fluctuations of energy in small subsystems of a hot and relativistic gas is derived. We find an increase in fluctuations for subsystems of small sizes, but we agrees with the energy fluctuations in the canonical ensemble if the size is large enough. Not only one can use our expression to find the limit of the concepts of energy density or fluid element in connection to relativistic heavy-ion collisions, but also in other areas of physics where one studies matter with high temperature and velocity.

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Natale, Gabriele, Thomas Bland, Simon Gschwendtner, Louis Lafforgue, Daniel S. Grün, Alexander Patscheider, Manfred J. Mark, and Francesca Ferlaino. "Bloch oscillations and matter-wave localization of a dipolar quantum gas in a one-dimensional lattice." Communications Physics 5, no. 1 (September 15, 2022). http://dx.doi.org/10.1038/s42005-022-01009-8.

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AbstractThree-dimensional quantum gases of strongly dipolar atoms can undergo a crossover from a dilute gas to a dense macrodroplet, stabilized by quantum fluctuations. Adding a one-dimensional optical lattice creates a platform where quantum fluctuations are still unexplored, and a rich variety of phases may be observable. We employ Bloch oscillations as an interferometric tool to assess the role quantum fluctuations play in an array of quasi-two-dimensional Bose-Einstein condensates. Long-lived oscillations are observed when the chemical potential is balanced between sites, in a region where a macrodroplet is extended over several lattice sites. Further, we observe a transition to a state that is localized to a single lattice plane–driven purely by interactions–marked by the disappearance of the interference pattern in the momentum distribution. To describe our observations, we develop a discrete one-dimensional extended Gross-Pitaevskii theory, including quantum fluctuations and a variational approach for the on-site wavefunction. This model is in quantitative agreement with the experiment, revealing the existence of single and multisite macrodroplets, and signatures of a two-dimensional bright soliton.

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Journal articles on the topic 'Supersolidity, quantum gas, quantum fluctuations'

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