Doublon-holon excitations split by Hund's rule coupling within the orbital-selective Mott phase

TL;DR

This paper investigates how Hund's rule coupling influences doublon-holon excitations in the orbital-selective Mott phase of a two-orbital Hubbard model, revealing how strong Hund's coupling alters in-gap states and quasiparticle peaks.

Contribution

It demonstrates the impact of Hund's rule coupling on interband doublon-holon bound states and quasiparticle spectra within the orbital-selective Mott phase using dynamical mean-field theory.

Findings

Interband doublon-holon bound states produce in-gap quasiparticle peaks.

Hund's rule coupling splits quasiparticle peaks and can move excitations outside the Mott gap.

Strong Hund's coupling suppresses orbital selectivity and restricts bound states.

Abstract

Multiorbital interactions have the capacity to produce an interesting kind of doublon-holon bound state that consists of a single-hole state in one band and a doubly-occupied state in another band. Interband doublon-holon pair excitations in the two-orbital Hubbard model are studied by using dynamical mean-field theory with the Lanczos method as the impurity solver. We find that the interband bound states may provide several in-gap quasiparticle peaks in the density of states of the narrow band in the orbital-selective Mott phase with a small Hund's rule coupling ($J$). There exists a corresponding energy relation between the in-gap states of the narrow band and the peaks in the excitation spectrum of the doublon for the wide band. We also find that the spin flip and pair-hopping Hund interactions can divide one quasiparticle peak into two peaks, where the splitting energy increases linearly with increasing $J$. Strong Hund's rule coupling can move the interband doublon-holon pair excitations outside the Mott gap and restrict the bound states by suppressing the orbital selectivity of the doubly-occupied and single-hole states.