Assymmetric features in the resistivity of clean quasi-one-dimensional systems: Fano resonances or non-Born effects?
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 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.