Superconductivity in the Hubbard model with correlated hopping: Slave-boson study

TL;DR

This study uses slave-boson mean-field theory to explore the phase diagram of the Hubbard model with correlated hopping, revealing how strong correlations influence superconductivity and phase transitions.

Contribution

It provides a comprehensive phase diagram for the Hubbard model with correlated hopping, highlighting the effects of strong correlations on superconductivity and phase transitions.

Findings

Superconductivity is stable near half-filling in strongly correlated regimes.

A direct transition from superconductor to Mott insulator occurs at half-filling.

Strong correlations alter the superconducting gap, making it nonexponential near phase transitions.

Abstract

The slave boson mean-field studies of the ground state of the Hubbard model with correlated hopping were performed. The approach qualitatively recovers the exact results for the case of the hopping integral t equal to the correlated hopping integral X. The phase diagram for the strongly correlated state with only singly occupied sites, the weakly correlated state, where single and double occupation is allowed, and for the superconducting state, was determined for any values of X and any electron concentration n. At the half-filled band (n=1) a direct transition from the superconductor to the Mott insulator was found. In the region of strong correlations the superconducting solution is stable for n close to 1, in contrast to the case of weak correlations, in which superconductivity occurs at n close to 0 and n close to 2. We found also that strong correlations change characteristics of the superconducting phase, e.g. the gap in the excitation spectrum has a nonexponential dependence close to the point of the phase transition.