Tunable Strongly Correlated Band Insulator

TL;DR

This paper introduces the concept of strongly correlated band insulators (SCI), exemplified by bilayer graphene, which can be tuned between SCI and weak coupling regimes, using a controllable 1/N expansion to analyze their properties.

Contribution

It defines the SCI concept and develops a 1/N expansion framework to study their observable properties, with bilayer graphene as a key example.

Findings

Bilayer graphene can be tuned between SCI and weak coupling regimes.

SCI features collective excitations (excitons) as lowest energy modes.

A controllable 1/N expansion effectively describes SCI properties.

Abstract

We introduce the notion of the strongly correlated band insulator (SCI), where the lowest energy excitations are collective modes (excitons) rather than the single particles. We construct controllable 1/N expansion for SCI to describe their observables properties. A remarkable example of the SCI is bilayer graphene which is shown to be tunable between the SCI and usual weak coupling regime.