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

TL;DR

This paper extends the quantum Gutzwiller approach to the two-component Bose-Hubbard model, analyzing quantum fluctuations' effects on phase transitions, superfluid properties, and interspecies drag, with relevance to experiments.

Contribution

It introduces a generalized quantum Gutzwiller method for the two-component Bose-Hubbard model and explores quantum fluctuation effects on phase diagram and dynamics.

Findings

Quantum fluctuations significantly affect interspecies drag near paired phases.

Quantum corrections influence coherence and density/spin fluctuations.

The approach provides insights into collective modes and correlations across phases.

Abstract

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.