Exotic Finite-Temperature Phase Diagram for Weakly Coupled S=1⁄2 XXZ Chain in a Magnetic Field

Abstract

We investigate the ordered state in S=1⁄2 XXZ spin chains with weak interchain couplings in a magnetic field by using quantum Monte Carlo simulations based on the directed-loop algorithm. The H–T phase diagram is illustrated for a square lattice and we find that an exotic spin-liquid state with quasi long-range incommensurate correlations in both the spin-chain and interchain directions may appear in the low-magnetization region without a finite-temperature transition. We also show that the incommensurate long-range-ordered state is stable for a cubic lattice.