Field theory of low energy excitations of a mixture of two species of pseudospin-1/2 Bose gases with interspecies spin-exchange

TL;DR

This paper develops a low energy effective field theory for a mixture of two pseudospin-1/2 Bose gases with interspecies spin-exchange, revealing four elementary excitations including a gapped mode, and discusses experimental detection via Bragg spectroscopy.

Contribution

It introduces a beyond single orbital-mode effective field theory capturing low energy excitations in a two-species pseudospin-1/2 Bose gas mixture with spin-exchange.

Findings

Identification of four elementary excitations, including a gapped mode.

Connection between the effective spin Hamiltonian spectrum and elementary excitations.

Potential for experimental measurement using Bragg spectroscopy.

Abstract

We develop a low energy effective field theory of a mixture of two species of pseudospin-1/2 atoms with interspecies spin-exchange, in addition to density-density interaction. This approach is beyond the single orbital-mode approximation. In a wide parameter regime, it indicates the existence of the four elementary excitations, especially a gapped mode due to interspecies spin-exchange. On the other hand, the spectrum of the effective spin Hamiltonian yielded by the single mode approximation can be obtained by quantizing the homogeneous excitation, which is spin excitation and is the long-wavelength limit of the gapped mode of elementary excitations. These low energy excitations can be experimentally measured by using Bragg spectroscopy.