Quantum Gutzwiller approach for the two-component Bose-Hubbard model

We study the effects of quantum fluctuations in the two-component Bose-Hubbard model generalizing to mixtures the quantum Gutzwiller approach introduced recently in [Phys. Rev. Research 2, 033276 (2020)]. As a basis for our study, we analyze the mean-field ground-state phase diagram and spectrum of elementary excitations, with particular emphasis on the quantum phase transitions of the model. Within the quantum critical regimes, we address both the superfluid transport properties and the linear response dynamics to density and spin probes of direct experimental relevance. Crucially, we find that quantum fluctuations have a dramatic effect on the drag between the superfluid species of the system, particularly in the vicinity of the paired and antipaired phases absent in the usual one-component Bose-Hubbard model. Additionally, we analyse the contributions of quantum corrections to the one-body coherence and density/spin fluctuations from the perspective of the collective modes of the system, providing results for the few-body correlations in all the regimes of the phase diagram. Copyright V. E. Colussi et al.

Automated summary

We study the effects of quantum fluctuations in the two-component Bose-Hubbard model and generalize the quantum Gutzwiller approach to mixtures. The mean-field ground-state phase diagram and spectrum of elementary excitations are analyzed, with a focus on quantum phase transitions. We investigate the superfluid transport properties and the linear response dynamics to density and spin probes within the quantum critical regimes. We find that quantum fluctuations have a significant impact on the drag between the superfluid species in the system, especially in the vicinity of the paired and antipaired phases absent in the usual one-component Bose-Hubbard model. Additionally, the contributions of quantum corrections to the one-body coherence and density/spin fluctuations are analyzed from the perspective of the collective modes of the system, providing results for the few-body correlations in all regimes of the phase diagram.