Dynamical response and competing orders in two-band Hubbard model

TL;DR

This study uses dynamical mean-field theory to analyze phase transitions and excitonic responses in a two-band Hubbard model, revealing continuous transitions, supersolid phases, and unique magnetic orderings.

Contribution

It provides new insights into the dynamical responses and phase transition mechanisms in the two-band Hubbard model, including the identification of a supersolid phase.

Findings

Continuous transition between excitonic condensate and spin-state order

Softening of excitonic mode at M-point signals approaching transition

Existence of a 2x2 magnetically ordered phase without normal phase precursor

Abstract

We present a dynamical mean-field study of two-particle dynamical response functions in two-band Hubbard model across several phase transitions. We observe that the transition between theexcitonic condensate and spin-state ordered state is continuous with a narrow strip of supersolidphase separating the two. Approaching transition from the excitonic condensate is announced bysoftening of the excitonic mode at theMpoint of the Brillouin zone. Inside the spin-state orderedphase there is a magnetically ordered state with 2x2 periodicity, which has no precursor in thenormal phase.