Low-energy interband Kondo bound states in orbital-selective Mott phases

TL;DR

This paper investigates low-energy excitations in the orbital-selective Mott phase of a two-orbital Hubbard model, revealing that inter-band Kondo-like bound states, rather than holon-doublon pairs, dominate the spectral features.

Contribution

It introduces a new understanding of low-energy excitations in OSMP, highlighting inter-band Kondo-like bound states over traditional holon-doublon bound states.

Findings

Holon-doublon bound states are incomplete for describing low-energy excitations.

Inter-band Kondo-like bound states dominate the spectral features.

Anomalous excitations appear as bandwidths of the two bands approach each other.

Abstract

Low-energy excitations in correlated electron systems may show intricate behaviors and provide essential insights into the dynamics of quantum states and phase transitions. Here, we study a typical half-filled two-orbital Hubbard model featuring the so-called holon-doublon (HD) low-energy excitations in the orbital-selective Mott phase (OSMP), where the principal form of the low-energy excitations has been considered to be a HD bound state. We employ standard single-site dynamical mean-field theory (DMFT), using NORG as an improved impurity solver to calculate the spectral functions at zero temperature. We show that the HD bound state gives an incomplete or even wrong picture for the low-energy excitations. Instead, the excitations are composed of a Kondo-like state in the wide band and a doublon in the narrow band, termed as inter-band Kondo-like (IBK) bound states. Remarkably, we find that, as the bandwidths of the two bands approach each other, anomalous IBK bound-state excitations appear in the metallic {\em wide} band. Our study provides a new picture for the low-energy excitations in the OSMP.