Subgap tunneling via quantum-interference effect: insulators and charge density waves

TL;DR

This paper explores quantum interference effects in subgap tunneling within insulators and charge density waves, explaining experimental magnetoresistance oscillations through a theoretical framework involving disorder and multichannel averaging.

Contribution

It introduces a novel interpretation of subgap tunneling effects, linking them to weak localization-like properties of evanescent quasiparticles rather than ground state interference.

Findings

Magnetoresistance oscillations with h/2e periodicity explained by quantum interference.

Subgap tunneling coupled to charge density wave sliding via charge accumulation.

Interference effects are attributed to evanescent quasiparticles, not ground state phenomena.

Abstract

A quantum interference effect is discussed for subgap tunneling over a distance comparable to the coherence length, which is a consequence of ``advanced-advanced'' and ``retarded-retarded'' transmission modes [Altland and Zirnbauer, Phys. Rev. B 55, 1142 (1997)]. Effects typical of disorder are obtained from the interplay between multichannel averaging and higher order processes in the tunnel amplitudes. Quantum interference effects similar to those occurring in normal tunnel junctions explain magnetoresistance oscillations of a CDW pierced by nanoholes [Latyshev et al., Phys. Rev. Lett. 78, 919 (1997)], having periodicity h/2e as a function of the flux enclosed in the nanohole. Subgap tunneling is coupled to the sliding motion by charge accumulation in the interrupted chains. The effect is within the same trend as random matrix theory for normal metal-CDW hybrids [Visscher et al., Phys. Rev. B 62, 6873 (2000)]. We suggest that the experiment by Latyshev et al. probes weak localization-like properties of evanescent quasiparticles, not an interference effect related to the quantum mechanical ground state.