Is the orbital-selective Mott phase stable against interorbital hopping?

TL;DR

This paper investigates the stability of the orbital-selective Mott phase (OSMP) in multiorbital systems against interorbital hopping, revealing that such hopping destabilizes OSMP at zero temperature, making it a crossover rather than a quantum critical point.

Contribution

The study demonstrates how interorbital hopping induces hybridization that destabilizes OSMP at zero temperature, providing analytical and numerical evidence within DMFT framework.

Findings

Interorbital hopping leads to hybridization, destabilizing OSMP at zero temperature.

The coherence scale is exponentially suppressed by interorbital hopping.

OSMP becomes a crossover, not a quantum critical point, at low temperatures.

Abstract

The localization-delocalization transition is at the heart of strong correlation physics. Recently, there is great interest in multiorbital systems where this transition can be restricted to certain orbitals, leading to an orbital-selective Mott phase (OSMP). Theoretically, the OSMP is widely studied for kinetically decoupled orbitals, but the effect of interorbital hopping remains unclear. Here, we show how nonlocal interorbital hopping leads to local hybridization in single-site dynamical mean-field theory (DMFT). Under fairly general circumstances, this implies that, at zero temperature, the OSMP, involving the Mott-insulating state of one orbital, is unstable against interorbital hopping to different, metallic orbital. We further show that the coherence scale below which all electrons are itinerant is very small and gets exponentially suppressed even if the interorbital hopping is not overly small. Within this framework, the OSMP with interorbital hopping may thus reach down to extremely low temperatures $T$, but not to $T=0$. Accordingly, it is part of a coherence-incoherence crossover and not a quantum critical point. We present analytical arguments supported by numerical results using the numerical renormalization group as a DMFT impurity solver. We also compare our findings with previous slave-spin studies.