Energy-gap analysis of quantum spin-glass transitions at zero temperature

Abstract

We study for random quantum spin systems the energy gap between the ground and first excited states to clarify a relation to the spin-glass-paramagnetic phase transition. We find that for the transverse Sherrington-Kirkpatrick model the vanishing of the averaged gap does not identify the transition. A power-law form of the gap distribution function leads to power-law distributions of the linear, spin-glass, and nonlinear susceptibilities. They diverge at different points, which we attribute to a quantum Griffiths mechanism. On the other hand, the classical treatment is justified for the transverse random energy model and the phase transition can be found by a sudden change of the ground state.

10 pages, 8 figures, Proceedings of the IW-SMI2010

Cited by in corpus (4)

• A Variational Ansatz for the Ground State of the Quantum Sherrington-Kirkpatrick Model
• Effects of low-lying excitations on ground-state energy and energy gap of Sherrington-Kirkpatrick model in transverse field
• Effects of dynamical paths on the energy gap and the corrections to free energy in path integrals of mean-field quantum spin systems
• Energy gap of quantum spin glasses: a projection quantum Monte Carlo study