The occurrence of a Mott-like gap in single-particle spectra of electron systems possessing flat bands

TL;DR

This paper demonstrates that flat-band strongly correlated electron systems can exhibit a Mott-like gap in single-particle spectra due to repulsive interactions and particle-hole symmetry violation, explaining Fermi arc phenomena in Sr$_2$IrO$_4$.

Contribution

It introduces a new type of Mott insulator in flat-band systems where the gap arises from quasiparticle interactions and symmetry violation, expanding understanding of correlated electron behavior.

Findings

Identification of a Mott-like gap linked to flat bands and repulsive interactions.

Explanation of Fermi arc structures in Sr$_2$IrO$_4$ without superconductivity.

Demonstration of gap formation due to particle-hole symmetry violation.

Abstract

An unconventional type of the Mott's insulators where the gap in the spectrum of single-particle excitations is associated with repulsive effective interactions between quasiparticles is shown to exist in strongly correlated electron systems of solids that possess flat bands. The occurrence of this gap is demonstrated to be the consequence of violation of particle-hole symmetry, inherent in such systems. The results obtained are applied to elucidate the Fermi arc structure observed at temperatures up to $100\,$ K in angle-resolved photoemission spectra of the compound Sr$_2$IrO$_4$, not showing superconductivity down to low $T$.