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DY: Dynamik und Statistische Physik
DY 46: Poster
DY 46.94: Poster
Thursday, March 27, 2003, 15:30–18:00, P1
Specific-heat and other critical exponents of random-field systems via ground-state calculations — •Alexander K. Hartmann1 and A. Peter Young2 — 1Institut für Theoretische Physik, Bunsenstraße 9, 37073 Göttingen, Germany — 2University of California, Santa Cruz CA 95064, USA
We calculate exact ground states of three- and four-dimensional random field Ising magnets (RFIM) with Gaussian distribution of the disorder using graph-theoretical algorithms. Systems for different strengths h of the random fields and sizes up to N∼ 106 are considered. We characterize the zero-temperature ferromagnetic-paramagnetic phase transitions in these models by studying magnetisation, Binder parameter, susceptibilities and a specific-heat like quantity. We obtain critical exponents describing the behavior of these quantities near the phase transition. Especially we find that the specific heat exhibits a cusp in three-dimensions [1], which agrees with results of Monte Carlo simulations of small systems, while it disagrees with results from experiments. In four dimensions the “specific heat” diverges logarithmically or slowly algebraically[2]. Finally we discuss several (hyper-) scaling relations.
[1] A. K. Hartmann and A. P. YoungPhys. Rev. B 64, 214419 (2001)
[2] A.K. HartmannPhys. Rev. B 65, 174427 (2002)