Random-field-driven ground-state phase transitions of the S = 1 XXZ spin chain

Yoshihiro Nishiyama

清美 岡本, Kiyomi Okamoto

Mounaim Hamdoune, Mohammed Daoud A

Yoshihiro Nishiyama

The ground state of the S=1 XXZ spin chain under the influence of the random magnetic field is studied by means of the exact diagonalization method. The S=12 counterpart has been investigated extensively so far. The easy-plane area, including the Haldane and the XY phases, is considered. The area suffers significantly from the magnitude of the constituent spin. Destruction of the Haldane state is observed at a critical strength of the random field, which is comparable to the magnitude of the Haldane gap. This transition is characterized by the disappearance of the string order. The XY region continues until at a critical randomness, at which a transition of the KT-universality class occurs. These features are contrasted with those of the S=12 counterpart.

Curtis A. Doty, Daniel S. Fisher

We analyze the zero-temperature phase diagram of the spin-1/2 quantum XXZ chain in the presence of weak disorder. The effects of various random perturbations are considered, including random fields and random exchange. For random perturbations that preserve the XY symmetry, we find a phase transition, as the anisotropy parameter is varied, from a ground state with quasi-long-range order (as in the pure system) to one in which typical correlation functions decay rapidly. The critical behavior at this transition is shown to be in the universality class of the Giamarchi-Schulz transition for one-dimensional bosons in a random potential. Random perturbations that break the XY symmetry are found always to destroy the quasi-long-range order of the ground state. Properties of the resulting random phases are also discussed.

Jenő Sólyom