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arXiv:2406.08902 · Physical Review A

Mutual dipolar drag in a bilayer Fermi gas

B. Renklioglu, Ben Yu-Kuang Hu, Mehmet Özgür Oktel, B. Tanatar

Published Jun 12, 2024• 1 citation
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Abstract

We consider two-dimensional spin-polarized dipolar Fermi gases confined in a double-layer system and calculate the momentum transfer between the layers as a function of temperature to investigate the transport properties of the system. We use the Hubbard approximation to describe the correlation effects and the screening between the dipoles within a single layer. The effective interlayer interaction between the dipoles across the layers is obtained by the random-phase approximation. We calculate the interaction strength and the layer separation distance dependence of the drag rate, and we show that there is a critical distance below which the system is unstable. In addition, we calculate the typical behavior of the collective modes related to the density fluctuations.

DOI
10.1103/physreva.109.063319

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We consider two-dimensional spin-polarized dipolar Fermi gases confined in a double-layer system and calculate the momentum transfer between the layers as a function of temperature to investigate the transport properties of the system. We use the Hubbard approximation to describe the correlation effects and the screening between the dipoles within a single layer. The effective interlayer interaction between the dipoles across the layers is obtained by the random-phase approximation. We calculate the interaction strength and the layer separation distance dependence of the drag rate, and we show that there is a critical distance below which the system is unstable. In addition, we calculate the typical behavior of the collective modes related to the density fluctuations.
We consider two parallel layers of two-dimensional spin-polarized dipolar Fermi gas without any tunneling between the layers. The effective interactions describing screening and correlation effects between the dipoles in a single layer (intra-layer) and across the layers (interlayer) are modeled within the Hubbard approximation. We calculate the rate of momentum transfer between the layers when the gas in one layer has a steady flow. The momentum transfer induces a steady flow in the second layer which is assumed initially at rest. This is the drag effect familiar from double-layer semiconductor and graphene structures. Our calculations show that the momentum relaxation time has temperature dependence similar to that in layers with charged particles which we think is related to the contributions from the collective modes of the system.
We consider a bilayer system of two-dimensional spin-polarized dipolar Fermi gas without any tunneling between the layers. We calculate the energy transfer rate between the layers in the non-linear regime where the layers have a relative velocity, as a function of temperature and drift velocities of the particles of the system in each layer. The effective interactions describing the correlation effects and screening between the dipoles are obtained by the Hubbard approximation in a single layer (intra-layer), and the random-phase approximation (RPA) across the layers (inter-layer). The energy transfer arises from the long-range nature of dipolar interactions between the particles of the system. As a result of the increasing drift velocities, the non-linear heat transfer between the layers remarkably increases and the system reaches its equilibrium at lower temperatures. Our calculations show that cooling with dipolar interactions without any material contact can be utilized to cool the ultracold dipolar systems.
We consider a bilayer of dipolar bosons in which the polarization of dipoles are perpendicular to the planes. Using accurate static structure factor S(q)S(q)S(q) data from hypernetted-chain calculation for single layer dipolar bosons we construct effective screened interactions for intralayer particles. We adopt the random-phase approximation for interlayer interactions. We study the instability of the homogeneous bilayer system against the formation of density waves by investigating the poles of the density-density response function. The dispersion of collective modes of this system also signals the density-wave instability. We also investigate the effect of counterflow on the collective mode dispersion and on the density-wave instability and discuss the dissipationless superfluid drag effect in the presence of a background velocity.
We investigate a dilute Fermi gas of polar molecules confined into a bilayer setup with dipole moments polarized perpendicular to the layers. In particular, we consider the extreme case of population imbalance, where we have only one particle in one layer and many particles in the other one. The single molecule is attracted by the dilute Fermi gas through the interlayer dipole-dipole force, presenting an interesting impurity problem with long-range anisotropic interaction. We characterize the quasiparticle, calculating its chemical potential with a Brueckner-Hartree-Fock approach. Moreover, we determine the momentum relaxation rate for finite momentum and temperature. The latter is reminiscent of Coulomb drag in bilayer electronic systems. For a confined system we relate the results for the chemical potential with the measurement of the oscillation frequency of the impurity. The momentum relaxation rate provides instead an estimate on how quickly the oscillations are damped.
We consider a bilayer of dipolar particles in which the polarization of dipoles is perpendicular to the planes, in the antiparallel configuration. Using accurate static structure factor data from hypernetted-chain (HNC) and Fermi HNC calculations, respectively for an isolated layer of dipolar bosons and dipolar fermions, we construct effective screened intralayer interactions. Adopting the random-phase approximation for interlayer interactions, we investigate the instability of these homogeneous bilayer systems towards the formation of density waves by studying the poles of the density–density response function. We have also studied the collective modes of these systems and find that the dispersion of their antisymmetric collective mode signals the emergence of the density wave instability as well.
We investigate the behavior of identical dipolar fermions with aligned dipole moments in two-dimensional multilayers at zero temperature. We consider density instabilities that are driven by the attractive part of the dipolar interaction and, for the case of bilayers, we elucidate the properties of the stripe phase recently predicted to exist in this interaction regime. When the number of layers is increased, we find that this ``attractive'' stripe phase exists for an increasingly larger range of dipole angles, and if the interlayer distance is sufficiently small, the stripe phase eventually spans the full range of angles, including the situation where the dipole moments are aligned perpendicular to the planes. However, in this regime, we expect the behavior to be strongly modified by the binding of dipoles between layers. In the limit of an infinite number of layers, we derive an analytic expression for the mean-field interlayer effects in the density-density response function and, using this result, we find that the stripe phase is replaced by a collapse of the dipolar system.