Zero-bias anomalies of point contact resistance due to adiabatic electron renormalization of dynamical defects

TL;DR

This paper investigates how adiabatic electron renormalization affects dynamical defects in ballistic metallic point contacts, leading to zero-bias resistance anomalies similar to those predicted by the Two Channel Kondo Model, but from a different physical basis.

Contribution

It introduces a new model for zero-bias anomalies based on electron renormalization of dynamical defects, distinct from the Two Channel Kondo Model.

Findings

Lower energy states contribute more to resistance than upper states.

Mesoscopic fluctuations cause defect energy splitting and resistance variation.

The model predicts zero-bias anomalies similar to TCKM predictions.

Abstract

We study effect of the adiabatic electron renormalization on the parameters of the dynamical defects in the ballistic metallic point contact. The upper energy states of the ``dressed'' defect are shown to give a smaller contribution to a resistance of the contact than the lower energy ones. This holds both for the "classical" renormalization related to defect coupling with average local electron density and for the "mesoscopic" renormalization caused by the mesoscopic fluctuations of electronic density the dynamical defects are coupled with. In the case of mesoscopic renormalization one may treat the dynamical defect as coupled with Friedel oscillations originated by the other defects, both static and mobile. Such coupling lifts the energy degeneracy of the states of the dynamical defects giving different mesoscopic contribution to resistance, and provides a new model for the fluctuator as for the object originated by the electronic mesoscopic disorder rather than by the structural one. The correlation between the defect energy and the defect contribution to the resistance leads to zero-temperature and zero-bias anomalies of the point contact resistance. A comparison of these anomalies with those predicted by the Two Channel Kondo Model (TCKM) is made. It is shown, that although the proposed model is based on a completely different from TCKM physical background, it leads to a zero-bias anomalies of the point contact resistance, which are qualitatively similar to TCKM predictions.