Regensburg 2000 – wissenschaftliches Programm
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DY: Dynamik und Statistische Physik
DY 23: Magnetismus und Spinsysteme
DY 23.4: Vortrag
Dienstag, 28. März 2000, 12:00–12:15, H3
(ENTFÄLLT) Random quantum magnets with long-range correlated disorder: Enhancement of critical and Griffiths-McCoy singularities — •Heiko Rieger 1 and Ferenc Iglói 2 — 1FB 10.1 Theoretische Physik, Universität des Saarlandes, 66041 Saarbrücken — 2Research Institute for Solid State Physics, 1525 Budapest, P.O.Box 49, Hungary
We study the effect of spatial correlations in the quenched disorder on random quantum magnets at and near a quantum critical point. In the random transverse field Ising systems disorder correlations that decay algebraically with an exponent ρ change the universality class of the transition for small enough ρ and the off-critical Griffiths-McCoy singularities are enhanced. We present exact results for 1d utilizing a mapping to fractional Brownian motion and generalize the predictions for the critical exponents and the generalized dynamical exponent in the Griffiths phase to d≥2.