Spin-glass effects in the critical phenomena

Naoki Kawashima, Takayuki Aoki

Amnon Aharony A, Y. Imry

Koji Hukushima

An efficient Monte Carlo method is extended to evaluate directly domain-wall free energy for randomly frustrated spin systems. Using the method, critical phenomena of Ising and Heisenberg spin glasses in three dimensions are investigated. Clear evidence of a finite-temperature spin-glass phase transition is presented in the Ising spin glass, while there is no such tendency in Heisenberg spin glass.

J. J. Préjean

M. Schmidt, N. Kellermann, Fábio M. Zimmer

We investigate a disordered cluster Ising antiferromagnet in the presence of a transverse field. By adopting a replica cluster mean-field framework, we analyze the role of quantum fluctuations in a model with competing short-range antiferromagnetic and intercluster disordered interactions. The model exhibits paramagnetic (PM), antiferromagnetic (AF), and cluster spin-glass (CSG) phases, which are separated by thermal and quantum phase transitions. A scenario of strong competition between AF and CSG unveils a number of interesting phenomena induced by quantum fluctuations, including a quantum PM state and quantum driven criticality. The latter occurs when the thermally driven PM-AF discontinuous phase transition becomes continuous at strong transverse fields. Analogous phenomena have been reported in a number of systems, but a description of underlying mechanisms is still required. Our results indicate that quantum driven criticality can be found in a highly competitive regime of disordered antiferromagnets, which is in consonance with recent findings in spin models with competing interactions.

Vladimir V. Prudnikov, G. B. Teǐtel'Baum