Strong effects of thermally induced low-spin-to-high-spin crossover on transport properties of correlated metals

TL;DR

This study uses dynamical mean-field theory to show how thermally induced low-spin-to-high-spin crossover significantly impacts the electrical transport properties of correlated metals, causing notable resistivity changes.

Contribution

It demonstrates the influence of thermal spin crossover on transport in multi-orbital correlated metals, highlighting effects on resistivity and conduction channels.

Findings

Resistivity can increase by a factor of three at high temperatures.

High-spin states significantly affect scattering and conduction.

Thermal activation of carriers influences magnetic response and transport.

Abstract

We use dynamical mean-field theory to study how electronic transport in multi-orbital metals is influenced by correlated (nominally) empty orbitals that are in proximity to the Fermi level. Specifically, we study 2 + 1 orbital and 3 + 2 orbital (i.e. t2g + eg ) models on a Bethe lattice with a crystal field that is set so that the higher lying orbitals are nearly empty at low temperatures but get a non-negligible occupancy at elevated temperature. The high temperature regime is characterized by thermal activation of carriers leading to higher magnetic response (i.e., thermally induced low-spin to high-spin transition) and substantial influence on resistivity, where one can distinguish two counteracting effects: increased scattering due to formation of high spin and increased scattering phase space on one hand, and additional parallel conduction channel on the other. The former effect is stronger and one may identify cases where resistivity increases by a factor of three at high temperatures even though the occupancy of the unoccupied band remains small (< 10%). We discuss implications of our findings for transport properties of correlated materials.