Magnetic State of the Geometrically Frustrated Quasi-One-Dimensional Spin System Cu$_3$Mo$_2$O$_9$ Studied by Thermal Conductivity

TL;DR

This study investigates the thermal conductivity of the frustrated quasi-one-dimensional spin system Cu$_3$Mo$_2$O$_9$ under magnetic fields, revealing spin contributions and field-induced changes linked to a potential novel spin state.

Contribution

It provides new insights into the magnetic field effects on thermal conductivity and suggests the existence of a novel field-induced spin state in a frustrated Mott insulator.

Findings

Spin contribution to thermal conductivity observed along spin chains.

Thermal conductivity decreases with magnetic field due to reduced spin gap.

Thermal conductivity increases at high fields, indicating a possible new spin state.

Abstract

We have measured the thermal conductivity of the geometrically frustrated quasi-onedimensional spin system Cu$_3$Mo$_2$O$_9$ in magnetic fields. A contribution of the thermal conductivity due to spins has been observed in the thermal conductivity along the spin chains. The thermal conductivity due to phonons, $\kappa_{\rm phonon}$, has been found to decrease by the application of a magnetic field, which has been explained as being due to the reduction in the spin gap originating from the spin-singlet dimers. Moreover, it has been found that $\kappa_{\rm phonon}$ increases with increasing field in high fields above ~7 T at low temperatures. This suggests the existence of a novel field-induced spin state and is discussed in terms of the possible spin-chirality ordering in a frustrated Mott insulator.