Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 25: Correlated Electrons - Poster Session
TT 25.41: Poster
Mittwoch, 29. März 2006, 14:30–18:30, P1
The spectral properties and the metal-insulator transition in the spin-fermion and s-d exchange model: equation of motion approach — •Andrey Katanin1,2 and Valentin Irkhin2 — 1Max-Planck-Institut für Festkörperforschung, 70569, Stuttgart, Germany — 2Institute of Metal Physics, 620219 Ekaterinburg, Russia
The classical s-d exchange and the spin-fermion models are studied within the equation-of-motion approach combined with the 1/N expansion (N is the number of spin components, N=3 for physical spins). The local and magnetic splitting in the electronic spectral functions is discussed. In the d→ ∞ limit, where only local fluctuations are important, the s-d model yields a metal-insulator transition with increasing interaction strength, while the spin-fermion model yields nonvanishing spectral weight at the Fermi level at any finite interaction. For d=2 in the presence of strong ferromagnetic fluctuations the self-energy at low temperatures T has a non-Fermi liquid form in the energy window |ω |< Δ 0 near the Fermi level, where Δ 0 is the spin splitting for magnetically ordered ground state, and Δ 0∝ T1/2ln1/2(vF/T) in the quantum critical regime (vF is the Fermi velocity). In the renormalized classical regime the spectral functions have a two-peak structure at finite T, which implies quasisplitting of the Fermi surface due to strong magnetic fluctuations. The role of dynamic spin fluctuations in the spin-fermion model is discussed.