Induced interactions in the BCS-BEC crossover of two-dimensional Fermi gases with Rashba spin-orbit coupling

Abstract

We investigate the Gorkov-Melik-Barkhudarov (GM) correction to superfluid transition temperature in two-dimensional Fermi gases with Rashba spin-orbit coupling (SOC) across the SOC-driven BCS-BEC crossover. In the calculation of the induced interaction, we find that the spin-component mixing due to SOC can induce both of the conventional screening and additional antiscreening contributions that interplay significantly in the strong SOC regime. While the GM correction generally lowers the estimate of transition temperature, it turns out that at a fixed weak interaction, the correction effect exhibits a crossover behavior where the ratio between the estimates without and with the correction first decreases with SOC and then becomes insensitive to SOC when it goes into the strong SOC regime. We demonstrate the applicability of the GM correction by comparing the zero-temperature condensate fraction with the recent quantum Monte Carlo results.

Entanglement between pairing and screening in the Gorkov-Melik-Barkhudarov correction to the critical temperature throughout the BCS-BEC crossover

“…To obtain this result, we have made use of the definition (6) for the regularized particle-particle bubble (with Q = 0) and of its approximate expression (10) valid in the BCS limit, as well as of the result ln(µ/T ) ≃ −π/(2k µ a F ) obtained by the Thouless criterion (9) in the absence of the Popov correction by assuming that T is of the order of the critical temperature T c . Entering the results (14) and (15) in Eq. (13) with Q = 0, we obtain eventually in the BCS limit…”

“…In practice, this was simply done by calculating the particle-hole bubble associated with particle-hole excitations (suitably averaged over the Fermi sphere, like in the original GMB calculation), but now with a chemical potential that spans the whole crossover and thus is no longer equal to E F (apart from minor differences resulting from the way the chemical potential itself is calculated [13,14]). Recently, extensions along these lines were also considered to investigate the GMB correction when including the effect of the Rashba spinorbit coupling in two-dimensional Fermi gases [15]. A completely different approach was instead followed in Ref.…”

Superconducting monolayer deposited on substrate: Effects of the spin-orbit coupling induced by proximity effects

“…It can be due to the fact that these peaks are located solely at the Fermi level for very small either electron or hole concentrations in the system (i.e., at n ≈ 0 or n ≈ 2, respectively). However, this behavior can have an important role in extremally dilute systems, e.g., in the BCS-BEC crossover region [81][82][83].…”