Spin Excitation Spectra of Spin-Orbit Coupled Bosons in Optical Lattice

TL;DR

This paper investigates the spin-wave excitation spectra of spin-orbit coupled two-component Bose gases in optical lattices, revealing gapless and gapped phases and suggesting potential new states due to spin fluctuations.

Contribution

It provides a detailed analysis of spin-wave spectra for various magnetic phases in spin-orbit coupled Bose gases, highlighting the destabilization of the skyrmion phase.

Findings

Vortex crystal phase has gapless linear dispersion.

Commensurate spiral and skyrmion crystal phases are gapped.

Spin fluctuations destabilize the skyrmion phase.

Abstract

Spin-wave excitation plays important roles in the investigation of the magnetic phases. In this paper, we study the spin-wave excitation spectra of two-component Bose gases with spin-orbit coupling on a deep square optical lattice using spin-wave theory. We find that, while the excitation spectrum of the vortex crystal phase is gapless with a linear dispersion in the vicinity of the minimum point, the spectra of the commensurate spiral spin phase and the skyrmion crystal phase are gapped. Significantly, the spin fluctuations strongly destabilize the classical ground state of the skyrmion phase. It suggests the emergence of a new state in the phase diagram. Such features of the spin excitation spectra provide further insights into the exploration of the exotic spin phases.