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Münster 1999 – scientific programme

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TT: Tiefe Temperaturen

TT 22: Quantenstörstellen und quantenkritische Ph
änomene

TT 22.5: Talk

Friday, March 26, 1999, 11:00–11:15, F3

Influence of locally ordered islands on a quantum phase transition — •T. Vojta1,2, R. Narayanan1, and D. Belitz11Department of Physics, University of Oregon, Eugene, OR 97403 — 2Institut für Physik, Technische Universität, D-09107 Chemnitz

We investigate the antiferromagnetic quantum phase transition of disordered itinerant electrons. In contrast to the standard formalism, which is based on integrating out the disorder at the very beginning by means of the replica trick, we take into account non-perturbative degrees of freedom coming from multiple local minima solutions of the mean-field equations. This leads to a new term in the effective action which substantially changes the renormalization group flow equations. In particular, we find that the critical fixed point which was found in the standard approach becomes unstable leading to runaway flow in the entire physically accessible parameter space. Possible interpretations of this runaway flow – non-existence of long-range order, a fluctuation-driven 1st order transition, or a transition to an inhomogeneously ordered phase – are discussed.

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