Unconventional superconductivity in a strongly correlated band-insulator without doping

TL;DR

This paper proposes a new method to achieve unconventional superconductivity in a strongly correlated band insulator without doping, by tuning interactions and frustration in the system.

Contribution

It introduces a theoretical model showing superconductivity arising in a correlated band insulator without doping, expanding understanding of unconventional SC mechanisms.

Findings

Superconductivity appears when interactions and band-gap are large and frustration suppresses magnetic order.

SC phase is sandwiched between a correlated band insulator and various magnetic metallic phases.

The model predicts multiple magnetic and metallic phases depending on interaction tuning.

Abstract

We present a novel route for attaining unconventional superconductivity (SC) in a strongly correlated system without doping. In a simple model of a correlated band insulator (BI) at half-filling we demonstrate, based on a generalization of the projected wavefunctions method, that SC emerges when e-e interactions and the bare band-gap are both much larger than the kinetic energy, provided the system has sufficient frustration against the magnetic order. As the interactions are tuned, SC appears sandwiched between the correlated BI followed by a paramagnetic metal on one side, and a ferrimagnetic metal, antiferromagnetic (AF) half-metal, and AF Mott insulator phases on the other side.