Europhys. Lett.
Volume 70, Number 6, June 2005
Page(s) 733 - 739
Section General
Published online 18 May 2005
Europhys. Lett., 70 (6), pp. 733-739 (2005)
DOI: 10.1209/epl/i2005-10042-2

Disorder-driven phase transitions of the large q-state Potts model in three dimensions

M. T. Mercaldo1, J.-Ch. Anglès d'Auriac2 and F. Iglói3, 4

1  Dipartimento di Fisica "E. R. Caianiello", Università degli Studi di Salerno and Laboratorio Regionale SuperMat INFM - I-84081 Baronissi (Salerno), Italy
2  Centre de Recherches sur les Trés Basses Températures B.P. 166, F-38042 Grenoble, France
3  Research Institute for Solid State Physics and Optics P.O. Box 49, H-1525 Budapest, Hungary
4  Institute of Theoretical Physics, Szeged University - H-6720 Szeged, Hungary

received 17 March 2005; accepted in final form 19 April 2005
published online 18 May 2005

Phase transitions induced by varying the strength of disorder in the large-q state Potts model in 3d are studied by analytical and numerical methods. By switching on the disorder, the transition stays of first order, but different thermodynamical quantities display essential singularities. Only for strong enough disorder will the transition be soften into a second-order one, in which case the ordered phase becomes non-homogeneous at large scales, while the non-correlated sites percolate the sample. In the critical regime the critical exponents are found universal: $\beta/\nu=0.60(2)$ and $\nu=0.73(1)$.

05.50.+q - Lattice theory and statistics (Ising, Potts, etc.).
64.60.Fr - Equilibrium properties near critical points, critical exponents.
75.10.Nr - Spin-glass and other random models.

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