Strong effects of weak localization in charge-density-wave/normal-metal hybrids

Abstract

Collective transport through a multichannel disordered conductor in contact with charge-density-wave electrodes is theoretically investigated. The statistical distribution function of the threshold potential for chargedensity-wave sliding is calculated by random matrix theory. In the diffusive regime weak localization has a strong effect on the sliding motion.Wave ͑Anderson͒ localization is an important concept of the quantum theory of electron transport. It is well established by now that a random disorder potential may cause bound states with an exponential decay governed by the localization length. When this localization length is large compared to other length scales in the system, the corrections to semiclassical transport are small, and the term ''weak localization'' is appropriate. Weak localization is well understood for normal Fermi liquids. However, localization in heterostructures like superconducting metal/normal metal ͑S/N͒, or Josephson ͑S/N/S͒ junctions is still actively investigated, experimentally and theoretically. For example, the electronhole coherence induced in a normal metal by a superconducting reservoir significantly modifies the weak localization correction to the electron transport through the hybrid structure. 1A charge-density wave ͑CDW͒ is a collective state similar to BCS superconductors ͑S͒.2 For instance, CDW reservoirs induce a proximity effect in normal metals ͑N͒ analogous to that in N/S junctions when the interface is parallel to the CD wave fronts ͑normal to the chains͒. In such a geometry the phase coupling through a defect-free CDW/N/CDW junction supports a sliding CDW mode.3 A process analogous to Andreev scattering at an N/CDW interface has been predicted. 4 Advances in thin film growth and patterning of CDW compounds 5 enables the study of CDW transport in various geometries on a mesoscopic scale.6,7 Quantum oscillations have been identified in the magnetoresistance of the CDW compound NbSe 3 in the presence of columnar defects.8 Electrical contacts that inject the current parallel to the CDW chains allow detailed studies of the subgap conductance. 9In this paper we report characteristic effects of weak localization on CDW sliding through a disordered conductor. In contrast to the extensive literature on semiconductor-or superconductor hybrid structures, 1 this topic has, to the best of our knowledge, not yet been investigated. The statistical properties of diffuse conductors, including the weaklocalization correction to the average conductance, are well described by random matrix theory. 10 We calculate the statistical properties of the pinning energy in the presence and absence of time-reversal symmetry by averaging over random transfer matrices. We find that the pinning strength is much more sensitive to the localization-enhanced backward scattering than the normal conductance. Weak localization is destroyed when time reversal-symmetry is broken by a magnetic field, 11 leading to a substantial negative magnetoresistance.We consider a disordered metal with length L an...

Subgap tunneling via a quantum interference effect: Insulators and charge density waves

“…The effect that we consider is not directly related to non linearities of the CDW phase Hamiltonian 20,21,22,23,24,25,26,27,28,29,30,31,32,33 . We reach consistency with Visscher et al 15 finding on the basis of random matrix theory an unexpected strong effect of weak localization for CDWs connected to a disordered normal electrode. The effects discussed below rely on a geometrical parameter being comparable to the coherence length, namely D ∼ ξ 0 for a nanohole of diameter D in a CDW film.…”

“…Previous approaches to related phenomena in CDWs were based on weak localization in normal metal-CDW hybrids in the framework of random matrix theory 15 , Aharonov-Bohm oscillations 16 , soliton tunneling 16,17 and permanent currents 18,19 . The effect that we consider is not directly related to non linearities of the CDW phase Hamiltonian 20,21,22,23,24,25,26,27,28,29,30,31,32,33 .…”