Asymmetric Features in the Resistivity of Clean Quasi-One-Dimensional Systems: Fano Resonances or Non-Born Effects?

Abstract

We show that experimentally observed complex line shapes of smeared Van Hove singularities in the resistivity of a quasi-one-dimensional system may be due to non-Born effects in scattering. At low concentration of impurities n < n_c ∝ |λ| with respect to scattering amplitude λ the non-Born effects are essential if the Fermi level is sufficiently close to singularity. The structure of the line shape depends on the sign of λ: for repulsion (λ>0) it is “plateau–minimum–maximum–plateau,” while for attraction (λ<0) it is “plateau–maximum–minimum–maximum–plateau.” In contrast with Fano-resonance scenario, complex structure of the line shape arises even in the absence of a resonant level.