Three-dimensional quantum phase diagram of the exact ground states of a mixture of two species of spin-1 Bose gases with interspecies spin exchange

TL;DR

This paper maps out the exact ground states and quantum phase diagram of a two-species spin-1 Bose gas mixture, revealing how interspecies and intraspecies spin exchanges influence quantum phases and phase transitions.

Contribution

It provides the first comprehensive analysis of the exact ground states and phase diagram for this complex spinor Bose gas mixture, including the effects of various spin exchange interactions.

Findings

Ground states are always disentangled with ferromagnetic or zero interspecies coupling.

Quantum phase transitions occur with changes in interspecies spin coupling.

Tuning interspecies coupling can circumvent phase transitions caused by intraspecies coupling sign changes.

Abstract

We find nearly all the exact ground states of a mixture of two species of spin-1 atoms with both interspecies and intraspecies spin exchanges in absence of a magnetic field. The quantum phase diagram in the three-dimensional parameter space and its two-dimensional cross sections are described. The boundaries where the ground states are either continuous or discontinuous are determined, with the latter identified as where quantum phase transitions take place. The two species are always disentangled if the interspecies spin coupling is ferromagnetic or zero. Quantum phase transitions occur when the interspecies spin coupling varies between antiferromagtic and zero or ferromagnetic while the two intraspecies spin couplings both remain ferromagnetic. On the other hand, by tuning the interspecies spin coupling from zero to antiferromagnetic and then back to zero, one can circumvent the quantum phase transition due to sign change of the intraspecies spin coupling of a single species, which is spin-decoupled with the other species with ferromagnetic intraspecies spin coupling. Overall speaking, interplay among interspecies and two intraspecies spin exchanges significantly enriches quantum phases of spinor atomic gases.