Slope-Reversed Mott Transition in Multiorbital Systems

TL;DR

This paper investigates a unique slope-reversed first-order Mott transition in a two-orbital Hubbard model, revealing how Hund's coupling influences phase behavior and local moment formation.

Contribution

It demonstrates the emergence of a slope-reversed Mott transition driven by Hund's coupling using dynamical mean-field theory and quantum Monte Carlo methods.

Findings

Discovery of slope-reversed first-order Mott transition.

Hund's coupling lowers the critical temperature of the transition.

Orbital-selective Mott phase shows frozen local moments.

Abstract

We examine finite-temperature phase transitions in the two-orbital Hubbard model with different bandwidths by means of the dynamical mean-field theory combined with the continuous-time quantum Monte Carlo method. It is found that there emerges a peculiar slope-reversed first-order Mott transition between the orbital-selective Mott phase and the Mott insulator phase in the presence of Ising-type Hund's coupling. The origin of the slope-reversed phase transition is clarified by the analysis of the temperature dependence of the energy density. It turns out that the increase of Hund's coupling lowers the critical temperature of the slope-reversed Mott transition. Beyond a certain critical value of Hund's coupling the first-order transition turns into a finite-temperature crossover. We also reveal that the orbital-selective Mott phase exhibits frozen local moments in the wide orbital, which is demonstrated by the spin-spin correlation functions.