Emergence and evolution of electronic modes with temperature in spin-gapped Mott and Kondo insulators

TL;DR

This paper investigates how electronic modes emerge and evolve within the band gap of strongly correlated insulators like Mott and Kondo insulators as temperature increases, revealing their origin, spectral weight changes, and relation to spin excitations.

Contribution

It provides a theoretical and numerical analysis of temperature-induced emergent modes in various models, clarifying their origin and spectral evolution in strongly correlated insulators.

Findings

Emergent modes gain spectral weight and form robust bands with increasing temperature.

The change in band structure reflects spin excitations and can be observed up to spin-excitation energies.

The study offers a fundamental understanding of temperature effects on the band structure of insulators with a spin gap.

Abstract

Electronic modes emerge within the band gap at nonzero temperature in strongly correlated insulators such as Mott and Kondo insulators, exhibiting momentum-shifted magnetic dispersion relations from the band edges. As the temperature increases, the emergent modes gain considerable spectral weights and form robust bands that differ from the zero-temperature bands. Here, the origin of the emergent modes, their relation to doping-induced modes, and how their spectral weights increase with temperature are clarified in the ladder and bilayer Hubbard models and one- and two-dimensional Kondo lattice models using effective theory for weak inter-unit-cell hopping and numerical calculations. The results indicate that the temperature-driven change in the band structure reflecting spin excitation, including the change in the number of bands, can be observed in various strongly correlated insulators even with a spin gap, provided that the temperature increases up to about spin-excitation energies. The controlled analyses developed in this study significantly contribute to the fundamental understanding of the band structure of strongly correlated insulators at nonzero temperature.