Finite-temperature properties of the extended Heisenberg model on a triangular lattice

Abstract

We present numerical results for the $J_1$-$J_2$ Heisenberg model on a triangular lattice at finite temperatures $T>0$. In contrast to unfrustrated lattices we reach much lower $T\sim 0.15J_1$. In static quantities the novel feature is a quite sharp low-$T$ maximum in the specific heat. Dynamical spin structure factor $S(\mathbf{q},\omega )$ allows for the extraction of the effective spin-wave energies ${\omega }_{\mathbf{q}}(T)$ and their damping ${\gamma }_{\mathbf{q}}(T)$. While for $J_2=0$ our results are consistent with $T=0$ spin ordering, $J_2/J_1\sim 0.1$ induces additional frustration with a signature of spin liquid ground state. In the latter case, results for spin-lattice relaxation rate indicate in the low-$T$ accesible regime on $1/T_1\propto T^{\alpha }$ with $\alpha \ge 1$, as observed in recent spin-liquid materials on a triangular lattice.

9 pages, 10 figures