SKM 2023 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 44: Poster: Statistical Physics

DY 44.7: Poster

Donnerstag, 30. März 2023, 13:00–16:00, P1

The Griffiths Phase: A Large Deviations Study — •Lambert Münster1, Martin Weigel1, and Alexander K. Hartmann21Institut für Physik, TU Chemnitz, 09107 Chemnitz, Germany — 2Institut für Physik, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany

For spin systems with quenched disorder, the Griffiths phase is the thermal region between the phase transition in the pure system and the corresponding transition in the disordered system. The standard example is a dilute ferromagnet, where a certain fraction of bonds is missing [1]. The physical behavior of this phase is characterized by large fluctuations in the order parameter which are visible in the tails of the distribution of the magnetic susceptibility. To directly investigate this property, we combine a large-deviation Monte Carlo sampling algorithm [2,3] with a Gaussian modified ensemble [4], thus allowing us to study the distribution of physical quantities on a much larger range of the support as compared to previous studies [5], i.e., in the region of exponential small probabilities. In addition to considering the susceptibility distribution we also study other observables such as the specific heat, thus shedding new light on this intriguing physical phenomenon.

[1] A. J. Bray, Phys. Rev. Lett. 59, 586 (1987).

[2] A. K. Hartmann, Phys. Rev. E 65, 056102 (2002).

[3] A. K. Hartmann, Eur. Phys. J. B 84, 627 (2011).

[4] T. Neuhaus, J. S. Hager, Phys. Rev. E 74, 036702 (2006).

[5] K. Hukushima, Y. Iba, J. Phys. 95, 012005 (2008).

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