Collective modes of spin-orbit-coupled Fermi gases in the repulsive regime

Abstract

We investigate the collective modes in the spin-orbit coupled Fermi gas with repulsive s-wave interaction. The interplay between spin-orbit coupling and atom-atom interactions plays the crucial role in the collective behaviors of Fermi gas. In contrast with ordinary Fermi liquid, spin-orbit coupled Fermi gas has strongly correlated spin and density excitations. Within the scheme of random phase approximation, we classify collective modes based on the symmetry group and determine their properties via the poles of corresponding correlation functions. Besides, the particle-hole continuum is obtained, where the imaginary part of these correlation functions become non-vanishing. We also propose an experimental protocol for detecting these collective modes and discuss corresponding experimental signatures in the ultracold Fermi gases experiment.

Intrinsic Damping of Collective Spin Modes in a Two-Dimensional Fermi Liquid with Spin-Orbit Coupling

“…Ω 3 in Fig. 1, right), [8][9][10][11] which correspond to oscillations of the three components of magnetization. Indices 1 − 3 label the Cartesian system with the 3 axis along the normal to the plane of a 2D electron gas.…”

“…As a result, several physical quantities become dependent on eei, such as the optical conductivity, 16 Drude weight, 17 and frequencies of collective spin modes, which play the role of Larmor frequencies in zero magnetic field. [8][9][10][11] In this Letter, we discuss another fundamentally new effect induced solely by SOC: intrinsic damping of collective spin modes in the uniform (q = 0) limit. Interactioninduced damping of collective modes is not, by itself, a new effect.…”

“…3,4 Combining many-body interactions with broken SU(2) symmetry, one obtains a special-"chiral"-kind of Fermi liquid (FL) [5][6][7] that supports a new type of collective modes, "chiral-spin waves"-oscillations of the spin density in zero magnetic field. [8][9][10][11] In the absence of SOC, electron-electron interaction (eei) 12 does not affect certain properties of an electron system given that some symmetries are preserved. For example, the conductivity and cyclotron-resonance frequency of a Galilean-invariant system are not affected by eei; same is true for the de Haas-van Alphen (dHvA) frequency in an isotropic system 13 and for the Larmor frequency in the presence of an SU(2)-symmetric interaction.…”

Itinerant magnetic phases and quantum Lifshitz transitions in a three-dimensional repulsively interacting Fermi gas with spin-orbit coupling

“…In the presence of SOC, the density fluctuation is coupled with the spin fluctuation [15]. We introduce the density-spin order parameter φ µ , µ = n, x, y, z to decouple the interaction term via a Hubbard-Stratonovich transformation.…”

“…However, there are still relatively few works in the repulsive side. In view of the tunability of weak to strong repulsive interaction in the current experiments [7][8][9][10], it becomes topical and important to investigate possible new many body phenomena due to the interplay between the SOC and the repulsive interactions [14][15][16][17][18][19].…”