Electron self-trapping in intermediate-valent SmB6

TL;DR

This paper investigates the complex low-temperature electron transport in SmB6, revealing that self-trapped electron-polaron complexes, influenced by valence fluctuations, explain its unusual resistivity and Hall effect behaviors.

Contribution

It introduces the concept that self-trapped electron-polaron complexes, rather than impurity band electrons, dominate low-temperature transport in SmB6, linked to valence fluctuations.

Findings

Identification of three energy scales in SmB6 affecting transport regimes

Demonstration that electron trapping involves interaction with valence fluctuations

Evidence that low-temperature conduction is due to electron-polaron complexes

Abstract

SmB6 exhibits intermediate valence in the ground state and unusual behaviour at low temperatures. The resistivity and the Hall effect cannot be explained either by conventional sf-hybridization or by hopping transport in an impurity band. At least three different energy scales determine three temperature regimes of electron transport in this system. We consider the ground state properties, the soft valence fluctuations and the spectrum of band carriers in n-doped SmB6. The behaviour of excess conduction electrons in the presence of soft valence fluctuations and the origin of the three energy scales in the spectrum of elementary excitations is discussed. The carriers which determine the low-temperature transport in this system are self-trapped electron-polaron complexes rather than simply electrons in an impurity band. The mechanism of electron trapping is the interaction with soft valence fluctuations.