Alternating S=1⁄2 XY Chain in the Lorentzian Random Field

Abstract

The alternating S=1⁄2 XY chain in the Lorentzian random field in the z-direction is investigated by the use of the pseudo-Fermion representation. The random-averaged one-particle Green’s functions for the pseudo-Fermions are exactly calculated, which enables us to exactly construct the thermodymanics of this model. The spin correlation function ⟨S_i^zS_j^z⟩ is also studied at T=0. The dimerized state (which is the ground state in the absence of the random field) is completely destroyed by any small (but finite) amount of the random field.