Thermodynamic properties of the quantum antiferromagnet on the triangular lattice in a magnetic field

We study the thermodynamic properties of the S = 1/2 quantum antiferromagnetic Heisenberg model on finite triangular lattices with N (less than or equal to 27) spins in a magnetic field using a quantum transfer Monte Carlo method. The size dependence of the order parameter suggests that a threshold (H(1)similar to 2.8J) exists, below which the long-range order is broken by the quantum fluctuation. For H>H-1, only the longitudinal component of the order parameter has a finite nonzero value at low temperatures. The transition temperature is estimated at different magnetic fields and the phase diagram is predicted.