Coherent quantum transport of charge density waves

TL;DR

This paper proposes a quantum transport model for charge density waves (CDWs) based on coherent soliton tunneling, explaining observed quantum oscillations and threshold behaviors, with implications for quantum computing applications.

Contribution

It introduces a Josephson-like tunneling model for CDWs using quantum solitons, linking microscopic tunneling to macroscopic quantum phenomena in CDW systems.

Findings

Observation of h/2e oscillations in conductance of CDW rings above 77 K

Interpretation of CDW threshold electric field as Coulomb blockade for soliton pairs

Potential for magnetic quantum interference and quantum computing applications

Abstract

Recent experiments show oscillations of dominant period h/2e in conductance vs. magnetic flux of charge density wave (CDW) rings above 77 K, revealing macroscopically observable quantum behavior. The time-correlated soliton tunneling model discussed here is based on coherent, Josephson-like tunneling of microscopic quantum solitons of charge 2e. The model interprets the CDW threshold electric field as a Coulomb blockade threshold for soliton pair creation, often much smaller than the classical depinning field but with the same impurity dependence (e.g., ~ ni^2 for for weak pinning). This picture draws upon the theory of time-correlated single-electron tunneling to interpret CDW dynamics above threshold. Similar to Feynman's derivation of the Josephson current-phase relation for a superconducting tunnel junction, the picture treats the Schrodinger equation as an emergent classical equation to describe the time-evolution of Josephson-coupled order parameters related to soliton dislocation droplets. Vector or time-varying scalar potentials can affect the order parameter phases to enable magnetic quantum interference in CDW rings or lead to interesting behavior in response to oscillatory electric fields. The ability to vary both magnitudes and phases is an aspect important to future applications in quantum computing.