title: Quantum-mechanically induced asymmetry in the phase diagrams of spin-glass systems.
abstract: The spin-1/2 quantum Heisenberg spin-glass system is studied in all spatial dimensions d by renormalization-group theory. Strongly asymmetric phase diagrams in temperature and antiferromagnetic bond probability p are obtained in dimensions d>or=3. The asymmetry at high temperatures approaching the pure ferromagnetic and antiferromagnetic systems disappears as d is increased. However, the asymmetry at low but finite temperatures remains in all dimensions, with the antiferromagnetic phase receding from the ferromagnetic phase. A finite-temperature second-order phase boundary directly between the ferromagnetic and antiferromagnetic phases occurs in d>or=6, resulting in a new multicritical point. In d=3, 4, 5, a paramagnetic phase reaching zero temperature intervenes asymmetrically between the ferromagnetic and reentrant antiferromagnetic phases. There is no spin-glass phase in any dimension.
authors.affiliation: Department of Physics, Koç University, Sariyer 34450, Istanbul, Turkey.
authors.forename: C Nadir
authors.initials: CN
authors.lastname: Kaplan
authors.forename: A Nihat
authors.initials: AN
authors.lastname: Berker