Variable-range hopping through marginally localized phonons

TL;DR

This paper studies how electrons coupled to marginally localized phonons in one dimension affect many-body localization, revealing a novel phonon exchange process that dominates low-temperature transport and alters traditional hopping mechanisms.

Contribution

It introduces a new understanding of phonon-mediated hopping in systems with marginally localized phonons, showing a divergence in phonon number exchange at low temperatures.

Findings

Variable-range hopping is suppressed at low temperatures due to bath discreteness.

Thermalization occurs via exchange of a diverging number of phonons, n∝-log T.

The phonon exchange process leads to a highly singular prefactor in Mott's formula.

Abstract

We investigate the effect of coupling Anderson localized particles in one dimension to a system of marginally localized phonons having a symmetry protected delocalized mode at zero frequency. This situation is naturally realized for electrons coupled to phonons in a disordered nano-wire as well as for ultra-cold fermions coupled to phonons of a superfluid in a one dimensional disordered trap. To determine if the coupled system can be many-body localized we analyze the phonon-mediated hopping transport for both the weak and strong coupling regimes. We show that the usual variable-range hopping mechanism involving a low-order phonon processes is ineffective at low temperature due to discreteness of the bath at the required energy. Instead, the system thermalizes through a many-body process involving exchange of a diverging number $n\propto -\log T$ of phonons in the low temperature limit. This effect leads to a highly singular prefactor to Mott's well known formula and strongly suppresses the variable range hopping rate. Finally we comment on possible implications of this physics in higher dimensional electron-phonon coupled systems.