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

Abstract

We study the thermodynamic properties of the $S=\frac{1}{2}$ quantum antiferromagnetic Heisenberg model on finite triangular lattices with $N (<~27)$ spins in a magnetic field using a quantum transfer Monte Carlo method. The size dependence of the order parameter suggests that a threshold ${(H}_{1}\ensuremath{\sim}2.8J)$ 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.