Hysteresis of noninteracting and spin-orbit-coupled atomic Fermi gases with relaxation

Abstract

Hysteresis can be found in driven many-body systems such as magnets and superfluids. Rate-dependent hysteresis arises when a system is driven periodically while relaxing towards equilibrium. A two-state paramagnet driven by an oscillating magnetic field in the relaxation approximation clearly demonstrates rate-dependent hysteresis. A noninteracting atomic Fermi gas in an optical ring potential, when driven by a periodic artificial gauge field and subjected to dissipation, is shown to exhibit hysteresis loops of atomic current due to a competition of the driving time and the relaxation time. This is in contrast to electronic systems exhibiting equilibrium persistent current driven by magnetic flux due to rapid relaxation. Universal behavior of the dissipated energy in one hysteresis loop is observed in both the magnetic and atomic systems, showing linear and inverse-linear dependence on the relaxation time in the strong and weak dissipation regimes. While interactions in general invalidate the framework for rate-dependent hysteresis, an atomic Fermi gas with artificial spin-orbit coupling exhibits hysteresis loops of atomic currents. Cold-atoms in ring-shape potentials are thus promising in demonstrating rate-dependent hysteresis and its associated phenomena.

Boundary-induced dynamics in one-dimensional topological systems and memory effects of edge modes

“…Quantum memory effects, however, are not unique to topological systems. When compared to previous studies utilizing a tunable bound state 22 , a flat-band of dispersionless states 21 , a competition between the characteristic times of driving and dissipation 23 , the memory effects in the topological models discussed here offer an additional realization for retaining information of dynamics.…”

“…For example, a competition of driving period and relaxation time leads to rate-dependent hysteresis, which is another manifestation of memory effects (see Ref. 23 and references therein). Here the intrinsic time scale is the hopping time determined by w. The edge mode is special in the sense that it is inside the energy gap between the two bands and brings a different energy scale.…”

“…In different models the dependence of the steady-state density on the rate of boundary transformation can be different. Memory effects have been proposed in noninteracting quantum systems possessing interesting properties such as a tunable bound state 22 , a geometric flat-band 21 , or rate-dependent hysteresis 23 . Here we show that memory effects from pure quantum dynamics should also be observable in edge-mode dynamics of topological models.…”

Engineered thermalization and cooling of quantum many-body systems

“…Despite this, most analog quantum simulation platforms typically focus on preparing pure quantum states of many-body systems. This is partly because preparing mixed states on many leading analog quantum simulation platforms, e.g., trapped cold atoms, is challenging due to the lack of scattering mechanisms needed to dissipate energy and thermalize [4,5]. Therefore, the thermalizing environment must be also engineered and simulated, which is challenging since such environments typically contain an immense number of degrees of freedom.…”

Quantification of the memory effect of steady-state currents from interaction-induced transport in quantum systems

“…Cold-atom systems with their broadly tunable parameters are suitable for elucidating key mechanisms behind quantum transport [26]. Memory effects, in the form of hysteresis, have been explored in cold-atom experiments of atomic superfluids [27] and theoretical proposal of spin-orbit coupled Fermi gases [28]. Energy dissipation has been included by vortex generation or external reservoirs in those hysteresis studies.…”