Spinon localization in the heat transport of the spin-1/2 ladder compound (C$_5$H$_{12}$N)$_2$CuBr$_4$

TL;DR

This study investigates how magnetic fields influence heat transport in a spin-1/2 ladder compound, revealing spinon localization effects that suppress thermal conductivity within the Luttinger-liquid state.

Contribution

It provides experimental evidence of spinon localization affecting heat transport in a spin ladder, highlighting the role of spinon-phonon interactions and field-induced localization phenomena.

Findings

Thermal conductivity is weakly affected by magnetic field-induced phase transitions.

Strong suppression of thermal conductivity occurs within the Luttinger-liquid state.

Spinon localization and spinon-phonon umklapp scattering explain the observed heat transport behavior.

Abstract

We present experiments on the magnetic field-dependent thermal transport in the spin-1/2 ladder system (C$_5$H$_{12}$N)$_2$CuBr$_4$. The thermal conductivity $\kappa(B)$ is only weakly affected by the field-induced transitions between the gapless Luttinger-liquid state realized for $B_{c1}< B < B_{c2}$ and the gapped states, suggesting the absence of a direct contribution of the spin excitations to the heat transport. We observe, however, that the thermal conductivity is strongly suppressed by the magnetic field deeply within the Luttinger-liquid state. These surprising observations are discussed in terms of localization of spinons within finite ladder segments and spinon-phonon umklapp scattering of the predominantly phononic heat transport.