Breakdown of Luttinger's theorem in two-orbital Mott insulators

TL;DR

This paper demonstrates that Luttinger's theorem does not generally hold for two-orbital Mott insulators, highlighting differences between Mott and band insulators through analysis of the Hubbard model.

Contribution

It reveals the breakdown of Luttinger's theorem in two-orbital Mott insulators and explores the adiabatic connection between different insulating phases.

Findings

Luttinger's theorem is invalid for generic Mott insulators.

Mott insulators have a Luttinger surface characterized by poles and zeros.

Ground states of different insulators with two electrons per unit cell are adiabatically connected.

Abstract

An analysis of Luttinger's theorem shows that -- contrary to recent claims -- it is not valid for a generic Mott insulator. For a two-orbital Hubbard model with two electrons per site the crossover from a non-magnetic correlated insulating phase (Mott or Kondo insulator) to a band insulator is investigated. Mott insulating phases are characterized by poles of the self-energy and corresponding zeros in the Greens functions defining a ``Luttinger surface'' which is absent for band insulators. Nevertheless, the ground states of such insulators with two electrons per unit cell are adiabatically connected.