Colossal enhancement of spin-chirality-related Hall effect by thermal fluctuation

The effect of thermal fluctuation on the spin-chirality-induced anomalous Hall effect in itinerant magnets is theoretically studied. Considering a triangular-lattice model as an example, we find that a multiple-spin scattering induced by the fluctuating spins increases the Hall conductivity at a finite temperature. The temperature dependence of anomalous Hall conductivity is evaluated by a combination of an unbiased Monte Carlo simulation and a perturbation theory. Our results show that the Hall conductivity can increase up to $10^3$ times the ground state value; we discuss that this is a consequence of a skew scattering contribution. This enhancement shows the thermal fluctuation significantly affects the spin-chirality-related Hall effect. Our results are potentially relevant to the thermal enhancement of anomalous Hall effect often seen in experiments.