Nonequilibrium spin fluctuations in single-electron transistors

TL;DR

This paper demonstrates that nonequilibrium spin fluctuations can significantly alter electronic transport in single-electron transistors, especially when spin relaxation is slow, leading to modified Coulomb steps and additional low-temperature resonances.

Contribution

The authors extend orthodox tunneling theory to include electron spin, revealing new transport phenomena caused by high-spin states and nonequilibrium spin fluctuations.

Findings

Spin fluctuations influence charge transport in single-electron transistors.

Modified Coulomb steps and low-temperature resonances are observed.

Experimental confirmation of predictions was achieved by Fujisawa et al.

Abstract

We show that nonequilibrium spin fluctuations significantly influence the electronic transport in a single-electron transistor, when the spin relaxation on the island is slow compared to other relaxation processes, and when size effects play a role. To describe spin fluctuations we generalize the `orthodox' tunneling theory to take into account the electron spin, and show that the transition between consecutive charge states can occur via a high-spin state. This significantly modifies the shape of Coulomb steps and gives rise to additional resonances at low temperatures. Recently some of our predictions were confirmed by Fujisawa et al. [Phys. Rev. Lett. 88, 236802 (2002)], who demonstrated experimentally the importance of nonequilibrum spin fluctuations in transport through quantum dots.