We investigate the phase diagram of asymmetric two-component Fermi gases at zero temperature as a function of polarization and interaction strength. The equations of state of the uniform superfluid and normal phase are determined using quantum Monte Carlo simulations. We find three different mixed states, where the superfluid and the normal phase coexist in equilibrium, corresponding to phase separation between (a) the polarized superfluid and the fully polarized normal gas, (b) the polarized superfluid and the partially polarized normal gas, and (c) the unpolarized superfluid and the partially polarized normal gas.
We investigate the phase diagram of a two-component repulsive Fermi gas at T=0 by means of quantum Monte Carlo simulations. Both purely repulsive and resonant attractive model potentials are considered in order to analyze the limits of the universal regime where the details of interatomic forces can be neglected. The equation of state of both balanced and unbalanced systems is calculated as a function of the interaction strength and the critical density for the onset of ferromagnetism is determined. The energy of the strongly polarized gas is calculated and parametrized in terms of the physical properties of repulsive polarons, which are relevant for the stability of the fully ferromagnetic state. Finally, we analyze the phase diagram in the interaction-polarization plane under the assumption that only phases with homogeneous magnetization can be produced.
We calculate the superfluid transition temperature of homogeneous interacting Bose gases in three and two spatial dimensions using large-scale Path Integral Monte Carlo simulations (with up to N = 10 5 particles). In 3D we investigate the limits of the universal critical behavior in terms of the scattering length alone by using different models for the interatomic potential. We find that this type of universality sets in at small values of the gas parameter na 10−4 . This value is different from the estimate na 3 10−6 for the validity of the asymptotic expansion in the limit of vanishing na 3 . In 2D we study the Berezinskii-Kosterlitz-Thouless transition of a gas with hard-core interactions. For this system we find good agreement with the classical lattice |ψ| 4 model up to very large densities. We also explain the origin of the existing discrepancy between previous studies of the same problem. PACS numbers:The theoretical determination of the superfluid transition temperature in homogeneous, interacting Bose systems is a fine example of a many-body problem that can be quantitatively addressed only by "exact" numerical techniques. This fact is well understood in the case of strongly interacting quantum fluids, such as liquid 4 He where the critical temperature in bulk [1] as well as in two-dimensional configurations [2, 3] was calculated using path integral Monte Carlo (PIMC) simulations, but at first glance is surprising in the case of dilute gases. However, in three dimensions (3D) the presence of any finite interaction changes the universality class of the transition from the Gaussian complex-field model, corresponding to the ideal gas Bose-Einstein condensation (BEC) temperature T 0 c , to that of the XY model. Thus, the critical temperature T c can not be obtained from T 0 c perturbatively [4]. In two dimensions (2D) the superfluid transition, which belongs to the Berezinskii-KosterlitzThouless (BKT) universality class [5,6], is induced by interaction effects and there is no unperturbed critical temperature to start with.In a 3D weakly repulsive gas the critical temperature shift is fixed by the s-wave scattering length a (a > 0), which characterizes interatomic interactions at low temperature [4,7,8,9,10,11,12,13],
We measure the magnetic susceptibility of a Fermi gas with tunable interactions in the low temperature limit and compare it to quantum Monte Carlo calculations. Experiment and theory are in excellent agreement and fully compatible with the Landau theory of Fermi liquids. We show that these measurements shed new light on the nature of the excitations of the normal phase of a strongly interacting Fermi gas.
Abstract. Aiming at simplicity of explicit equations and, at the same time, controllable accuracy of the theory, we present our results for all the thermodynamic quantities and correlation functions for a weakly interacting Bose gas at short-to-intermediate distances obtained within an improved version of Beliaev's diagrammatic technique. With a controllably small (but essentially finite) Bogoliubov's symmetry-breaking term, Beliaev's diagrammatic technique becomes regular in the infrared limit. Up to higher-order terms (for which we present parametric order-of-magnitude estimates), the partition function and entropy of the system formally correspond to those of a non-interacting bosonic (pseudo-)Hamiltonian with a temperature-dependent Bogoliubov-type dispersion relation. Away from the fluctuation region, this approach provides the most accurate-in fact, the best possible within the Bogoliubov-type pseudoHamiltonian framework-description of the system with controlled accuracy. It produces accurate answers for the off-diagonal correlation functions up to distances where the behavior of correlators is controlled by generic hydrodynamic relations and, thus, can be accurately extrapolated to arbitrarily large scales. In the fluctuation region, the non-perturbative contributions are given by universal 7
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.