Low temperature transport in tunnel junction arrays: Cascade energy relaxation

TL;DR

This paper develops a theory for low-temperature, far-from-equilibrium electron transport in tunnel junction arrays, highlighting a cascade energy relaxation process involving bosonic environments and phonons, and its impact on tunneling current.

Contribution

It introduces a novel cascade two-stage energy relaxation model for tunnel junction arrays at low temperatures, incorporating environmental bosonic modes and phonon interactions.

Findings

Energy relaxation can occur via a two-stage cascade process.

Opening the environmental excitation gap suppresses tunneling current.

Derived current-voltage characteristics for the arrays.

Abstract

A theory of far-from-equilibrium transport in arrays of tunnel junctions is developed. We show that at low temperatures the energy relaxation ensuring tunneling current can become a cascade two-stage process. First, charge carriers lose their energy to a bosonic environment via non-phonon energy exchange. The role of such an environment can be taken by electromagnetic fluctuations or dipole excitations (electron-hole pairs). The environment, in its turn, relaxes the energy to the thermostat by means of phonon irradiation. We derive the current-voltage characteristics for the arrays and demonstrate that opening the energy gap in the spectrum of the environmental excitations completely suppresses the tunneling current. The consequences of the cascade relaxation in various physical systems are discussed.