MONTE-CARLO SIMULATIONS OF RESONATING-VALENCE-BOND U(1) DYNAMICS

In the auxiliary-field formulation of Baskaran and Anderson, and of Nakamura and Matsui for the t-J model including cases with weak interlayer hoppings, Monte Carlo simulations are performed with respect to U(1) phase dynamics of nearest-neighbor singlet annihilation operators. Parameters fixed throughout simulations are the intralayer hopping, t = 0.3 eV, and nearest-neighbor antiferromagnetic coupling, J = 0.1 eV. Thermal-cycle simulations are performed for various values of parameters, interlayer hopping, 0 less-than-or-equal-to t' less-than-or-equal-to 0.06 eV, and hole density, 0.005 less-than-or-equal-to delta- less-than-or-equal-to 0.07, and phase transitions are observed. The transitions exhibit phase coherence up to global U(1) rotation in the low-temperature phase, but the phase configurations show that they are of the flux phase, violating time-reversal and parity symmetry invariance. For small-delta, a nonperiodic flux phase is observed. The transitions are basically those violating the discrete symmetries due to the frustration of the forces involved.