Magnetothermal transport in the spin-1/2 chains of copper pyrazine dinitrate

TL;DR

This study investigates how magnetic fields influence thermal conductivity in a spin-1/2 chain compound, revealing unexpected features that challenge existing theoretical models of spin excitations.

Contribution

The paper provides experimental evidence of field-dependent thermal transport anomalies in copper pyrazine dinitrate, highlighting a field-independent mean free path of spin excitations in the quantum critical regime.

Findings

Thermal conductivity exhibits a dip at low magnetic fields, likely due to Umklapp scattering.

A plateau-like feature appears in the quantum critical regime, indicating a constant mean free path.

The observed behavior contradicts theoretical predictions of field-dependent spin excitation scattering.

Abstract

We present experiments on the thermal transport in the spin-1/2 chain compound copper pyrazine dinitrate Cu(C_4 H_4 N_2)(NO_3)_2. The heat conductivity shows a surprisingly strong dependence on the applied magnetic field B, characterized at low temperatures by two main features. The first one appearing at low B is a characteristic dip located at mu_B B ~ k_B T, that may arise from Umklapp scattering. The second one is a plateau-like feature in the quantum critical regime, mu_B |B-B_c| < k_B T, where B_c is the saturation field at T=0. The latter feature clearly points towards a momentum and field independent mean free path of the spin excitations, contrary to theoretical expectations.