Europhys. Lett., 73 (5), pp. 779-785 (2006)
DOI: 10.1209/epl/i2006-10001-5

Finite-size scaling in Villain's fully frustrated model and singular effects of plaquette disorder

J. Lukic¹, E. Marinari² and O. C. Martin<sup>3

1</sup>  Dipartimento di Fisica, SMC and UdR1 of INFM Università di Roma "La Sapienza" - P.le Aldo Moro 2, 00185 Roma, Italy
²  Dipartimento di Fisica, INFN, Università di Roma "La Sapienza" P.le Aldo Moro 2, 00185 Roma, Italy
³  Laboratoire de Physique Théorique et Modèles Statistiques Bâtiment 100, Université Paris-Sud, F-91405 Orsay, France

received 24 October 2005; accepted in final form 5 January 2006
published online 25 January 2006

Abstract
The ground state and low-T behavior of two-dimensional spin systems with discrete binary couplings are subtle but can be analyzed using exact computations of finite-volume partition functions. We first apply this approach to Villain's fully frustrated model, unveiling an unexpected finite-size scaling law. Then we show that the introduction of even a small amount of disorder on the plaquettes dramatically changes the scaling laws associated with the T=0 critical point.

PACS
75.10.Nr - Spin-glass and other random models.
75.40.-s - Critical-point effects, specific heats, short-range order.
75.40.Mg - Numerical simulation studies.

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