Stability of the spontaneous quantum Hall state in the triangular Kondo-lattice model.

We study the behavior of the quarter-filled Kondo-lattice model on a triangular lattice by combining a zero-temperature variational approach and finite-temperature Monte Carlo simulations. For intermediate coupling between itinerant electrons and classical moments S(j), we find a thermodynamic phase transition into an exotic spin ordering with uniform scalar spin chirality and (S(j))=0. The state exhibits a spontaneous quantum Hall effect. We also study how its properties are affected by the application of an external magnetic field.