Evidence of one-dimensional magnetic heat transport in the triangular-lattice antiferromagnet Cs₂CuCl₄

We report on low-temperature heat-transport properties of the spin-1/2 triangular-lattice antiferromagnet Cs₂CuCl₄. Broad maxima in the thermal conductivity along the three principal axes, observed at about 5 K, are interpreted in terms of the Debye model, including the phonon Umklapp scattering. For thermal transport along the b axis, we found a pronounced field-dependent anomaly, close to the transition into the three-dimensional long-range-ordered state. No such anomalies were observed for the transport along the a and c directions. We argue that this anisotropic behavior is related to an additional heat-transport channel through magnetic excitations, that can best propagate along the direction of the largest exchange interaction. Our observations strongly support the quasi-1D spin-liquid scenario with spinons as elementary excitations, proposed for this frustrated antiferromagnet. Besides, peculiarities of the heat transport of Cs₂CuCl₄ in magnetic fields up to the saturation field and above are discussed.