Excitation spectra of a Bose-Einstein condensate with an angular spin-orbit coupling

TL;DR

This paper investigates the low-lying excitation spectra of a Bose-Einstein condensate with angular spin-orbit coupling, revealing unique dynamical behaviors and mode frequencies influenced by interactions and phase transitions.

Contribution

It provides a detailed analysis of excitations in a half-skyrmion phase using Bogoliubov and numerical methods, highlighting differences from other phases.

Findings

Complex two-dimensional center of mass motion after trap shift

Breathing mode frequency depends on spin-orbit coupling and interactions

Interaction effects are significant at phase transition

Abstract

A theoretical model of a Bose-Einstein condensate with angular spin-orbit coupling has recently been proposed and it has been established that a half-skyrmion represents the ground state in a certain regime of spin-orbit coupling and interaction. Here we investigate low-lying excitations of this phase by using the Bogoliubov method and numerical simulations of the time-dependent Gross-Pitaevskii equation. We find that a sudden shift of the trap bottom results in a complex two-dimensional motion of the system's center of mass that is markedly different from the response of a competing phase, and comprises two dominant frequencies. Moreover, the breathing mode frequency of the half-skyrmion is set by both the spin-orbit coupling and the interaction strength, while in the competing state it takes a universal value. Effects of interactions are especially pronounced at the transition between the two phases.