Regensburg 2000 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 19: Metall-Isolatorüberg
änge

TT 19.3: Vortrag

Donnerstag, 30. März 2000, 10:15–10:30, H18

Rare regions, local moments, and annealed disorder: A novel mechanism for metal-insulator transitions — •Thomas Vojta^1,2, Dietrich Belitz², and Theodore R. Kirkpatrick³ — ¹Institut für Physik, TU Chemnitz, D-09107 Chemnitz, Germany — ²Department of Physics and Materials Science Institute, University of Oregon, Eugene, OR 97403, USA — ³Institute for Physical Science and Technology, and Department of Physics, University of Maryland, College Park, MD 20742, USA

We show that local magnetic moments in disordered electronic systems can be described in terms of annealed magnetic disorder, i.e. magnetic disorder that is in thermal equilibrium with the rest of the system. This annealed magnetic disorder is generically self-generated in quenched disordered systems. We then develop a method for incorporating these ‘annealed local moments’ into a transport theory. As an example we consider a model system of non-interacting electrons with local magnetic moments. We show that the annealed magnetic disorder leads to a new mechanism, and a new universality class, for a metal-insulator transition. The transition is driven by a vanishing of the thermodynamic density susceptibility rather than by localization effects. The critical behavior in d=2+є dimensions is determined, and the underlying physics is discussed.