Regensburg 1998 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 21: Postersitzung III: Spin-Peierls-Systeme, Metall-Isolator-Übergang, Lokalisierung; SL: Theorie; Quantenflüssigkeiten und -kristalle; Amorphe Materialien, Tunnelsysteme; Borcarbide, Fullerene, konventionelle SL; SL dünner Filme; Experimentiertechniken
TT 21.22: Poster
Donnerstag, 26. März 1998, 15:00–18:30, D
Effective field theory for many fermion systems — •F. Evers1, D. Belitz2, and T. Kirkpatrick3 — 1Universitaet Karlsruhe, Kaiserstr. 12, 76128 Karlsruhe — 2University of Oregon — 3University of Maryland
A general field theoretical description of many-fermion systems is presented. The theory is valid for both short-ranged and Coulombic electron-electron interactions, and it allows for treating systems with or without quenched disorder. We perform a symmetry analysis, identify the soft modes, and integrate out the massive modes in an approximation that preserves the symmetries. In the disordered case, this allows for a technically satisfactory derivation of Finkel’stein’s generalization of Wegner’s nonlinear sigma-model. We use renormalization group methods to establish the existence of a Fermi-liquid fixed point and show that it is stable for d>2 and d>1 in the clean and disordered cases, respectively. The so called weak-localization effects, and analogous effects in clean systems, can be understood as the leading corrections to scaling near these fixed points. In addition to the well-known weak-localization nonanalyticities, we find nonanalytic corrections to the wave number dependent spin susceptibility that have consequences for the theory of ferromagnetism (see T. Vojta et. al, cond-mat/961109). (This work has been supported by NSF under grant numbers DMR-96-32978 and DMR-95-10185)