Magnetic instability of the orbital-selective Mott phase

TL;DR

This paper investigates the magnetic properties of the orbital-selective Mott phase in a two-orbital Hubbard model, revealing a ferromagnetic instability driven by Hund's coupling and characterizing the metallic band as a singular Fermi liquid.

Contribution

It demonstrates that the orbital-selective Mott phase exhibits a ferromagnetic instability for any nonzero Hund's rule exchange, using dynamical mean-field theory and effective spin models.

Findings

Ferromagnetic instability exists for any nonzero Hund's exchange.

The metallic band acts as a singular Fermi liquid with a logarithmic self-energy singularity.

The phase can be understood via an effective spin-1 Kondo Hamiltonian.

Abstract

We characterize the low-energy physics of the two-orbital Hubbard model in the orbital-selective Mott phase, in which one band is metallic and the other insulating. Using dynamical mean-field theory with the numerical renormalization group at zero temperature, we show that this phase has a ferromagnetic instability for any nonzero Hund's rule exchange interaction, which can be understood in terms of an effective spin-1 Kondo Hamiltonian. The metallic band therefore behaves as a singular Fermi liquid for which the self-energy has a logarithmic singularity at the Fermi energy.