Variable-Range Hopping of Spin Polarons: Magnetoresistance in a Modified Mott Regime

TL;DR

This paper investigates how spin polarons hop in disordered materials, revealing that at low temperatures, resistivity follows a non-activation law due to variable-range hopping, challenging traditional models.

Contribution

It introduces a model showing that in disordered solids, spin polaron hopping leads to non-activation resistivity behavior, diverging from standard Mott law predictions.

Findings

Resistivity obeys a non-activation law at low temperatures.

Hard polaron gap does not affect transport properties.

Hopping distance increases as temperature decreases.

Abstract

We analize electrical conductivity controlled by hopping of bound spin polarons in disordered solids with wide distributions of electron energies and polaron shifts (barriers). By means of percolation theory and Monte Carlo simulations we have shown that in such materials at low temperatures, when hopping occurs in the vicinity of the Fermi level, a hard polaron gap does not manifest itself in the transport properties. This happens because as temperature decreases the hopping polaron trades the decreasing electron and polaron barriers for increasing hopping distance. As a result, in the absence of the Coulomb correlation effects, in this variable-range variable-barrier hopping regime, the electrical resistivity as a function of temperature obeys a non-activation law, which differs from the standard Mott law.