Binary mixture of pseudospin-1/2 Bose gases with interspecies spin exchange: from classical fixed points and ground states to quantum ground states

TL;DR

This paper studies a mixture of two pseudo-spin-1/2 Bose gases with interspecies spin exchange, analyzing classical fixed points, quantum ground states, and entanglement properties, revealing how classical bifurcations relate to quantum entanglement.

Contribution

It provides a comprehensive analysis of classical and quantum ground states, stability, and entanglement in a two-species pseudospin-1/2 Bose gas system with interspecies spin exchange, including the effects of quantum fluctuations.

Findings

Classical fixed points' stability influences quantum dynamics.

Ground states are determined considering quantum fluctuations.

Maximal entanglement occurs at classical bifurcation points, especially in excited states.

Abstract

We consider the effective spin Hamiltonian describing a mixture of two species of pseudo-spin-1/2 Bose gases with interspecies spin exchange. First we analyze the stability of the fixed points of the corresponding classical dynamics, of which the signature is found in quantum dynamics with a disentangled initial state. Focusing on the case without an external potential, we find all the ground states by taking into account quantum fluctuations around the classical ground state in each parameter regime. The nature of entanglement and its relation with classical bifurcation is investigated. When the total spins of the two species are unequal, the maximal entanglement at the parameter point of classical bifurcation is possessed by the excited state corresponding to the classical fixed point which bifurcates, rather than by the ground state.