Ground-State Phase Diagram of the Two-Dimensional Quantum Heisenberg Mattis Model

Abstract

The two-dimensional $S=1/2$ asymmetric Heisenberg Mattis model is investigated with the exact diagonalization of finite clusters. The Néel order parameter and the spin glass order parameter can be smoothly extrapolated to the thermodynamic limit in the antiferromagnetic region, as in the pure Heisenberg antiferromagnet. The critical concentration of the Néel phase is consistent with that of the two-dimensional Ising Mattis model, and the spin glass order parameter increases monotonously as the ferro-bond concentration increases. These facts suggest that quantum fluctuation does not play an essential role in two-dimensional non-frustrated random spin systems. KEYWORDS: quantum spin system, ground state, randomness, Mattis model, Néel order, spin glass order

10 pages, LaTeX, 6 compressed/uuencoded postscript figures, J. Phys. Soc. Jpn. 65 (1996) No. 2 in press

References in corpus (3)

• Disorder Induced Phase Transition in a Random Quantum Antiferromagnet
• Numerical Study of a Two-Dimensional Quantum Antiferromagnet with Random Ferromagnetic Bonds
• Ground-State Phase Diagrams of the Two-Dimensional Quantum Heisenberg Spin Glass Models