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

Abstract

We develop a low energy effective field theory of a mixture of two species of pseudospin- atoms with interspecies spin exchange, in addition to density–density interaction. Thisapproach is beyond the single-orbital-mode approximation. In a wide parameterregime, it indicates the existence of the four elementary excitations, especially thegapped mode due to interspecies spin exchange. The spectrum of the effectivespin Hamiltonian yielded by the single-mode approximation can be obtainedby quantizing the homogeneous excitation, which is spin excitation and is thelong-wavelength limit of the gapped mode among the elementary excitations.These low energy excitations may be experimentally detected by using Braggspectroscopy.