Coexistence of two kinds of superfluidity in Bose-Hubbard model with density-induced tunneling at finite temperatures

TL;DR

This paper investigates the extended Bose-Hubbard model with density-induced tunneling, revealing the coexistence of two superfluid phases and their phase separation at finite temperatures using a quantum rotor approach.

Contribution

It demonstrates the mapping of the model to a pseudospin Hamiltonian and identifies conditions for coexistence and separation of superfluid phases, including the effects of density-induced tunneling.

Findings

Existence of two coexisting superfluid phases: single-particle and pair superfluidity.

Identification of parameter ranges with only pair superfluidity, no single-particle superfluidity.

Density-induced tunneling enhances coherence at high densities and low temperatures.

Abstract

With use of the U(1) quantum rotor method in the path integral effective action formulation, we have confirmed the mathematical similarity of the phase Hamiltonian and of the extended Bose-Hubbard model with density-induced tunneling (DIT). Moreover, we have shown that the latter model can be mapped to a pseudospin Hamiltonian that exhibits two coexisting (single-particle and pair) superfluid phases. Phase separation of the two has also been confirmed, determining that there exists a range of coefficients in which only pair condensation, and not single-particle superfluidity, is present. The DIT part supports the coherence in the system at high densities and low temperatures, but also has dissipative effects independent of the system's thermal properties.