Berlin 2024 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 29: Focus Session: Recent Progresses in Criticality in the Presence of Boundaries and Defects II (joint session DY/TT)
DY 29.4: Vortrag
Mittwoch, 20. März 2024, 16:00–16:15, A 151
The Griffiths phase and beyond: a large deviations study — •Lambert Münster1, Alexander K. Hartmann2, and Martin Weigel1 — 1Institut für Physik, TU Chemnitz, 09107 Chemnitz, Germany — 2Institut für Physik, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
The Griffiths phase is a temperature range in systems with quenched disorder that reaches from the critical temperature of the pure system to the corresponding critical temperature in the presence of disorder. In this phase, the possibility of large fluctuations in the disorder degrees of freedom leads to broad distributions in response functions. For example, inside the Griffiths phase of the two-dimensional bond-diluted Ising model the distribution of the magnetic susceptibility is expected to have an exponential tail [1]. A large-deviation Monte Carlo algorithm is used to sample this distribution [2,3], and the exponential tail is extracted over a wide range of the support down to probabilities of the order of 10−300. A connection between the local fraction of ferromagnetic bonds and the size of the magnetic susceptibility is demonstrated numerically. Furthermore the distribution of the magnetic susceptibility is also investigated at the ferromagnetic phase transition, inside the ferromagnetic phase and at zero temperature, revealing interesting differences and similarities between the cases.
[1] A. J. Bray, Phys. Rev. Lett. 59, 586 (1987).
[2] A. K. Hartmann, Phys. Rev. E 65, 056102 (2002).
[3] K. Hukushima, Y. Iba, J. Phys. Conf. Ser. 95, 012005 (2008).
Keywords: diluted ferromagnet; Griffiths phase; large deviations