Large thermomagnetic effects in weakly disordered Heisenberg chains

TL;DR

This paper theoretically predicts a significant dip in thermal conductivity of weakly disordered Heisenberg chains at a magnetic field around the temperature, due to the interplay of impurity and Umklapp scattering.

Contribution

It introduces a new theoretical understanding of how weak impurity and Umklapp scattering interact to produce observable dips in thermal conductivity in spin chains.

Findings

Thermal conductivity shows a pronounced dip at B ~ T in weakly disordered chains.

Reduction in heat transport can exceed 50% in clean samples.

The theory may explain recent experimental observations in copper pyrazine dinitrate.

Abstract

The interplay of different scattering mechanisms can lead to novel effects in transport. We show theoretically that the interplay of weak impurity and Umklapp scattering in spin-1/2 chains leads to a pronounced dip in the magnetic field dependence of the thermal conductivity $\kappa$ at a magnetic field $B \sim T$. In sufficiently clean samples, the reduction of the magnetic contribution to heat transport can easily become larger than 50% and the effect is predicted to exist even in samples with a large exchange coupling, J >> B, where the field-induced magnetization is small. Qualitatively, our theory might explain dips at $B \sim T$ observed in recent heat transport measurements on copper pyrazine dinitrate, but a fully quantitative description is not possible within our model.