Novel order parameter to describe the critical behavior of Ising spin glass models

FEDERICO J. ROMÁ, F. Nieto, Antonio Jose Ramirez-Pastor +1 more

A. Oubelkacem, A. Ainane, Juan José de Miguel +2 more

Bikas K. Chakrabarti

In view of the indications of nontrivial quantum effects on the spin-glass ground-state (frustration, etc.) properties, the Ising spin-glass models (both frustrated and unfrustrated) are investigated here in the presence of a transverse field to study the possible quantum effect on the corresponding (classical) Ising spin-glass behavior. Studies on the critical behavior show similar quantum effects as observed in other established second-order transitions.

Katarzyna Walasek, K. Lukierska‐Walasek

A mean-field approximation is used to investigate the quantum transverse Ising spin-glass model in the Edwards-Anderson version. We introduce two order parameters, diagonal and off diagonal in replica indices, and discuss their physical significance. The effective free-energy function is obtained, and the critical value of the transverse field $\ensuremath{\Gamma}$ at zero temperature is calculated. We find the behavior of the order parameters near the zero-temperature critical point. The phase diagram in the $\ensuremath{\Gamma}$,$T$ plane is also given.

Rajiv R. P. Singh

Dietrich Stauffer, Kurt Binder