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

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 $T \sim 0.15 J_1$. In static quantities the novel feature is a quite sharp low-$T$ maximum in the specific heat. Dynamical spin structure factor $S({\bf q},\omega)$ allows for the extraction of the effective spin-wave energies $\omega_{\bf q}(T)$ and their damping $\gamma_{\bf q}(T)$. 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 $\alpha \geq 1$, as observed in recent spin-liquid materials on a triangular lattice.