Orbital-selective Mott transitions in two-band Hubbard models

TL;DR

This paper uses advanced quantum Monte Carlo simulations within dynamical mean-field theory to reveal two distinct orbital-selective Mott transitions in a two-band Hubbard model, providing new insights into quantum criticality and non-Fermi-liquid phases.

Contribution

It demonstrates the occurrence of two separate OSMTs in an anisotropic two-orbital Hubbard model without spin-flip Hund exchange and introduces a generalized Hamiltonian for further analysis.

Findings

Two orbital-selective Mott transitions occur at a bandwidth ratio of 2.

Numerical errors in previous data are quantified, clarifying the second transition.

Insights into the nature of non-Fermi-liquid OSM phases and quantum-critical points are provided.

Abstract

The anisotropic two-orbital Hubbard model is investigated at low temperatures using high-precision quantum Monte Carlo (QMC) simulations within dynamical mean-field theory (DMFT). We demonstrate that two distinct orbital-selective Mott transitions (OSMTs) occur for a bandwidth ratio of 2 even without spin-flip contributions to the Hund exchange, and we quantify numerical errors in earlier QMC data which had obscured the second transition. The limit of small inter-orbital coupling is introduced via a new generalized Hamiltonian and studied using QMC and Potthoff's self-energy functional method, yielding insight into the nature of the OSMTs and the non-Fermi-liquid OSM phase and opening the possibility for a new quantum-critical point.