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Conductivity in a symmetry-broken phase: Spinless fermions with 1/ d corrections

1996; American Physical Society; Volume: 54; Issue: 15 Linguagem: Inglês

10.1103/physrevb.54.10436

1095-3795

Götz S. Uhrig,

Quantum and electron transport phenomena

The dynamic conductivity \ensuremath{\sigma}(\ensuremath{\omega}) of strongly correlated electrons in a symmetry-broken phase is investigated in the present work. The model considered consists of spinless fermions with repulsive interaction on a simple cubic lattice. The investigated symmetry-broken phase is the charge density wave (CDW) with wave vector Q=(\ensuremath{\pi},\ensuremath{\pi},\ensuremath{\pi}${)}^{\mathrm{\ifmmode\dagger\else\textdagger\fi{}}}$ which occurs at half-filling. The calculations are based on the high dimensional approach, i.e., an expansion in the inverse dimension 1/d is used. The finite dimensionality is accounted for by the inclusion of linear terms in 1/d and the true finite dimensional DOS. Special care is paid to the setup of a conserving approximation in the sense of Baym/Kadanoff without inconsistencies. The resulting Bethe-Salpeter equation is solved for the dynamic conductivity in the nonsymmetry-broken and in the symmetry-broken phase (AB-CDW). The dc-conductivity is reduced drastically in the CDW. Yet it does not vanish in the limit T\ensuremath{\rightarrow}0 due to a subtle cancellation of diverging mobility and vanishing DOS. In the dynamic conductivity \ensuremath{\sigma}(\ensuremath{\omega}) the energy gap induced by the symmetry breaking is clearly discernible. In addition, the vertex corrections of order 1/d lead to an excitonic resonance lying within the gap. \textcopyright{} 1996 The American Physical Society.