Phase diagram of exciton condensate in doped two-band Hubbard model

TL;DR

This study explores the phase diagram of exciton condensates in a doped two-band Hubbard model, revealing various phase transitions and magnetic properties using dynamical mean-field theory.

Contribution

It provides a detailed analysis of excitonic phases and their transitions near the spin-state change, including the discovery of a multi-critical point and magnetization switching.

Findings

Identification of all symmetry-allowed spin-triplet excitonic phases

Observation of first-order and continuous phase transitions

Discovery of a multi-critical point and magnetization switching mechanism

Abstract

Using the dynamical mean-field approximation we investigate formation of excitonic condensate in the two-band Hubbard model in the vicinity of the spin-state transition. With temperature and band filling as the control parameters we realize all symmetry allowed spin-triplet excitonic phases, some exhibiting a ferromagnetic polarization. While the transitions are first-order at low temperatures, at elevated temperatures continuous transitions are found that give rise to a multi-critical point. Rapid but continuous transition between ferromagnetic and non-magnetic excitonic phases allows switching of uniform magnetization by small changes of chemical potential.