Critical properties and phase diagram of the quantum anisotropic XY spin chain in a random magnetic field: A density-matrix renormalization-group analysis

摘要

The spin-1/2 quantum anisotropic XY spin chain in a transverse randommagnetic field parallel to the z axis is numerically studied by means of thedensity-matrix renormalization group. The dependence of the spontaneousmagnetization and the energy gap on both the strength of the random magneticfield and the factor of anisotropy is determined. The critical line for theorder-disorder phase transition is obtained and the resulting phase diagram isdrawn. Our results are compatible with the fact that models with differentfactors of anisotropy fall within the same universality class as the quantumIsing model in a transverse random field.