Electron spin blockade and singlet-triplet transition in a silicon single electron transistor

TL;DR

This paper studies a silicon single-electron transistor under magnetic fields, revealing spin blockade effects, singlet-triplet transitions, and the influence of Zeeman splitting on electron transport.

Contribution

It demonstrates the magnetic field dependence of electron states and spin blockade phenomena in a silicon SET, highlighting the role of Coulomb interaction and Zeeman effect.

Findings

Spin blockade reduces conductance by a factor of 8 at low fields.

Singlet-triplet transition lifts spin blockade at higher fields.

Zeeman splitting dominates the magnetic field dependence up to 9 T.

Abstract

We investigate a silicon single-electron transistor (SET) in a metal-oxide-semiconductor (MOS) structure by applying a magnetic field perpendicular to the sample surface. The quantum dot is defined electrostatically in a point contact channel and by the potential barriers from negatively charged interface traps. The magnetic field dependence of the excitation spectrum is primarily driven by the Zeeman effect. In the two-electron singlet-triplet (ST) transition, electron-electron Coulomb interaction plays a significant role. The evolution of Coulomb blockade peaks with magnetic field B is also owing to the Zeeman splitting with no obvious orbital effect up to 9 T. The filling pattern shows an alternate spin-up-spin-down sequence. The amplitude spectroscopy allows for the observation of the spin blockade effect, where the two-electron system forms a singlet state at low fields, and the spin polarized injection from the lead reduces the tunneling conductance by a factor of 8. At a higher magnetic field, due to the ST transition, the spin blockade effect is lifted and the conductance is fully recovered.