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.