Nanoscale phase separation and superconductivity in the one-dimensional Hirsch model

TL;DR

This study numerically explores the one-dimensional Hirsch model, revealing nanoscale phase separation, spin gaps, and superconductivity near half filling, with a crossover to homogeneous phases at certain correlated hopping values.

Contribution

It uncovers the emergence of nanoscale phase separation and superconductivity in the Hirsch model, highlighting the role of correlated hopping and filling in these phenomena.

Findings

Nanoscale phase separation occurs for x > 2/3 near half filling.

The NPS phase exhibits a spin gap and behaves as a Luther-Emery Liquid.

A charge structure factor peak relates to droplet size in NPS phase.

Abstract

We investigate numerically at various fillings the ground state of the one-dimensional Hubbard model with correlated hopping x (Hirsch model). It is found that, for a wide range of filling values n around half filling, and for repulsive Coulomb interaction u\leq u_c(x,n), phase separation at a nanoscale (NPS phase) between two conducting phases at different densities occurs when x\gtrsim 2/3. The NPS phase is accompanied by the opening of a spin gap and the system behaves as a Luther-Emery Liquid with dominant superconducting correlations. Close to half filling, an anomalous peak emerges in the charge structure factor related to the density of doubly occupied sites, which determines the size of the droplets in the NPS phase. For 1/2\lesssim x\lesssim 2/3 a crossover to a homogeneous phase, still superconducting, takes place.