Anisotropic dynamic excitations of a two-dimensional weakly interacting Fermi superfluid gas with Raman-type spin–orbit coupling
Shuning Tan, Jiayi Shi, Peng Zou +2 more
Abstract Exploring anisotropic dynamics in exotic superconductors or superfluids with spin–orbit coupling (SOC) is essential for understanding the role of SOC in these systems. We theoretically calculate the density dynamical structure factor of a two-dimensional Fermi superfluid with Raman-type SOC and investigate its primary anisotropic dynamical characteristics under varying SOC strengths during the Lifshitz phase transition. Owing to the recoil momentum of the SOC laser beam, both the collective phonon mode and the single-particle excitations exhibit distinct anisotropic behavior. In contrast to superfluids without SOC, the phonon mode under SOC not only has a shorter lifetime due to stronger competition with single-particle excitations but also exhibits an anisotropic sound velocity. The sound velocity initially decreases and then increases as the SOC strength increases. Moreover, three types of threshold energies for single-particle excitations to break Cooper pairs are identified, which elucidate the complex edge curves of the dynamical structure factor.
Communications in Theoretical Physics•May 26, 2026•0 citations