Effects of diagonal disorder on Charge Density Wave and Superconductivity in local pair systems

TL;DR

This paper investigates how diagonal disorder affects charge density waves and superconductivity in local pair systems, revealing various phases and phenomena like disorder-induced superconductivity and charge ordering.

Contribution

It extends previous mean field studies to arbitrary particle concentrations and maps out phase diagrams including new disorder-induced phenomena.

Findings

Identification of multiple phases including CDW, SS, Bose-glass, and phase separation.

Discovery of disorder-induced superconductivity and charge ordering.

Qualitative agreement with Monte Carlo results for 2D lattice.

Abstract

We analyse the influence of diagonal disorder (random site energy) on Charge Density Wave (CDW) and Superconductivity (SS) in local pair systems which are described by the model of hard core charged bosons on a lattice. This problem was previously studied within the mean field approximation for the case of half filled band (n = 1). Here we extend that investigation to the case of arbitrary particle concentration (0 < n < 2) and examine the phase diagrams of the model and the behaviour of superfluid density as a function of n and the increasing disorder. Depending on the strength of random on-site energies, the intersite density-density repulsion and the concentration the model can exhibit several various phases, including homogeneous phases: CDW, SS and Bose-glass (NO) as well as the phase separated states: CDW-SS, CDW-NO and particle droplets. The obtained results for SS phase are in qualitative agreement with the available Monte Carlo calculations for two dimensional lattice. Also, in a definite range of parameters the system exhibits the phenomena which we call a disorder induced superconductivity and a disorder induced charge ordering.