Münster 1999 – scientific programme

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TT: Tiefe Temperaturen

TT 15: Postersitzung II: Elektronische Eigenschaften (1-12), Josephson-Kontakte (13-27), Heavy Fermions (28-40), Theorie HTSL (41-48), M-I-Überg
änge, Korrelierte Systeme (49-79)

TT 15.70: Poster

Wednesday, March 24, 1999, 14:30–18:00, Foy

Electrical Conductivity and Magnetic Order in the Single-Band Hubbard-Model — •T. Herrmann¹, R. Kosimow², W. Borgieł², and W. Nolting¹ — ¹Institut f"ur Physik, Humboldt-Universit"at zu Berlin — ²Department of Theoretical Physics, Silesian University, Poland

A “modified alloy analogy” (MAA) for the single-band Hubbard model is used to investigate the interplay of ferromagnetic order and electrical conductivity in a system of itinerant band electrons. The alloy analogy is evaluated within the framework of the “coherent potential approximation” (CPA). The tensor conductivity, normally a two-particle Green function, can be represented by single-particle terms if CPA-consistent approaches are applied (Velický 1969).

The MAA is used for fcc and bcc lattices. Spontaneous ferromagnetism appears in the fcc lattice for a more than half-filled energy band (1<n<2). In the bcc lattice collective order is restricted to a small n-region. The electrical conductivity is investigated for different Coulomb strengths U as function of band occupation n and temperature T. The conductivity turns out to be substantially higher in the ferromagnetic than in the paramagnetic phase, even diverging in the case of ferromagnetic saturation (T→ 0), where electron-electron iscattering is excluded. The electrical resistivity exhibits a power-like low-temperature behavior becoming critical at T_C. Formal similarity to the spin disorder resistivity of local moment systems is observed.