Charge relaxation resistance in the cotunneling regime of multi-channel Coulomb blockade: Violation of Korringa-Shiba relation

TL;DR

This paper investigates the low-frequency admittance of a metallic island in the cotunneling regime, revealing temperature-dependent charge relaxation resistance and violation of the Korringa-Shiba relation at finite temperatures.

Contribution

It demonstrates the temperature dependence of charge relaxation resistance and shows the violation of the Korringa-Shiba relation in multi-channel Coulomb blockade cotunneling.

Findings

Charge relaxation resistance varies strongly with temperature.

At zero temperature, the resistance vanishes, confirming previous analyses.

The admittance does not satisfy the Korringa-Shiba relation at finite temperatures.

Abstract

We study the low frequency admittance of a small metallic island coupled to a gate electrode and to a massive reservoir via a \emph{multi channel} tunnel junction. The ac current is caused by a slowly oscillating gate voltage. We focus on the regime of inelastic cotunneling in which the dissipation of energy (the real part of the admittance) is determined by two-electron tunneling with creation of electron-hole pairs on the island. We demonstrate that at finite temperatures but low frequencies the energy dissipation is ohmic whereas at zero temperature it is super-ohmic. We find that (i) the charge relaxation resistance (extracted from the real part of the admittance) is strongly temperature dependent, (ii) the imaginary and real parts of the admittance do not satisfy the Korringa-Shiba relation. At zero temperature the charge relaxation resistance vanishes in agreement with the recent zero temperature analysis [M. Filippone and C. Mora, Phys. Rev. B {\bf 86}, 125311 (2012) and P. Dutt, T. L. Schmidt, C. Mora, and K. Le Hur, Phys. Rev. B {\bf 87}, 155134 (2013)].