Three-Component Ultracold Fermi Gases with Spin-Orbit Coupling

Abstract

We investigate the pairing physics in a three-component Fermi-Fermi mixture, where a few fermionic impurities are immersed in a non-interacting two-component Fermi gas with synthetic spin-orbit coupling (SOC), and interact attractively with one spin species in the Fermi gas. Due to the interplay of SOC and spin-selective interaction, the molecular state intrinsically acquires a non-zero center-of-mass momentum, which results in a new type of Fulde-Ferrell (FF) pairing in spin-orbit coupled Fermi systems. The existence of the Fermi sea can also lead to the competition between FF-like molecular states with different center-of-mass momenta, which corresponds to a first-order transition between FF phases in the thermodynamic limit. As the interaction strength is tuned, a polaron-molecule transition occurs in the highly imbalanced system, where the boundary varies non-monotonically with SOC parameters and gives rise to the reentrance of polaron states. The rich physics in this system can be probed using existing experimental techniques.

Impurity in a Fermi gas under non-Hermitian spin–orbit coupling

“…For the many-body setting, we assume that the Fermi energy is larger than the peak of the central barrier of the lower helicity branch, but smaller than the lowest energy of the higher helicity branch, so that only a single Fermi surface exists in the system. The actual Fermi energy E h is then a function of total density, as well as the SOC parameters [38]. An impurity interacts with the spin-up component of the Fermi sea, with the Hamiltonian…”

Critical temperature in the BCS-BEC crossover with spin-orbit coupling

“…The approximation scheme that we will employ is based again on the expansion of the action in the gap field, as in Eq. (62). The zeroth order is equivalent to the mean field approximation.…”

Topological superradiant state in Fermi gases with cavity induced spin–orbit coupling

“…For example, Fig. 7 is calculated at a temperature of k B T = E r /30 (T ∼ 118 nK for 6 Li atoms), and with a weaker cavity-atom coupling g A ∼ 4.3 MHz, a larger single-photon detuning ∆ = 10 GHz, and a larger cavity decay rate κ ∼ 14.8 MHz. Hence, the TSR phase should persist under typical experimental conditions.…”

“…When the atomic states are coupled with Raman lasers, the internal and external degrees of freedom of the atoms are also coupled. This effective SOC interaction modifies the single-particle dispersion spectra and can lead to novel quantum states in both the few-body [4][5][6] and many-body settings [7][8][9][10][11][12][13][14]. Of particular interest is the possibility of preparing and probing topological states in cold atomic gases under synthetic SOC.…”