Dynamical topological phases in quenched spin-orbit coupled degenerate Fermi gas

TL;DR

This paper explores how quenched spin-orbit coupled Fermi gases can exhibit various dynamical topological phases, characterized by distinct order parameter behaviors and edge states, expanding understanding beyond ground state properties.

Contribution

It introduces the concept of dynamical topological phases in quenched Fermi gases and classifies three distinct phases based on order parameter dynamics and topological features.

Findings

Identification of three dynamical phases: undamped, Landau damped, and over-damped.

Prediction of topological Floquet states with multiple edge modes in the undamped phase.

Observation that order parameter decay behaviors correlate with different topological boundary states.

Abstract

The spin-orbit coupled degenerate Fermi gas provides a totally new platform to realize topological superfluids and related topological excitations. Previous studies have mainly focused on the properties of the ground state. Here we consider a two-dimensional Fermi gas with Rashba spin-orbit coupling subject to a perpendicular Zeeman field. For this system, we have found that its ground state topological structure is captured by the spin texture, which is readily measurable in experiments. We show that, when the Zeeman field is suddenly quenched, dynamical topological phases can be realized. More specifically, three post-quench dynamical phases can be identified according to the asymptotic behavior of the order parameter. In the undamped phase, a persistent oscillation of the order parameter may support a topological Floquet state with multiple edge states. In the Landau damped phase, the magnitude of the order parameter approaches a constant via a power-law decay, and this system can support a dynamical topological phase with a pair of edge states at the boundary. In the over-damped phase, the order parameter decays to zero exponentially although the condensate fraction remains finite. These predictions can be observed in the strong coupling regime of ultracold Fermi gas.