Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot

TL;DR

This study demonstrates valley-enhanced Rabi frequency in a silicon quantum dot, revealing electric-dipole transitions and strong spin-valley coupling, which could enable fast all-electrical spin control.

Contribution

It reports the observation of valley-enhanced Rabi frequency and electric-dipole transitions in silicon quantum dots, advancing spin control techniques.

Findings

Enhanced Rabi frequency near valley anti-crossing due to electric-dipole transition.

Reconstructed energy-level diagram of a four-state spin-valley system.

Strong modulation of inter-valley spin coupling by magnetic field orientation.

Abstract

Electron spin resonance spectroscopy (ESR) of a single electron in planar Si-MOS quantum dot is reported in the vicinity of a valley level anti-crossing. A number of one and two-photon resonances are observed due to mixing of magnetic spin-flip and electric valley-flip transitions. This allows the reconstruction of the energy-level diagram of a four state system with two valley and two spin states. Near the anti-crossing, an enhancement of the Rabi frequency is observed. This is attributed to an electric-dipole transition activated by admixing of the upper energy level due to inter-valley spin coupling. The electric-dipole transition may be driven via capacitive coupling between the ESR antenna, and the confinement gate. To characterize spin-valley coupling responsible for the enhancement, we measure the anisotropy of the g-factor difference between the two valley states, the mean g-factor and the inter-valley spin coupling for both in and out-of-plane magnetic fields. The inter-valley spin coupling is strongly modulated by the direction of the B-field, and is strongest for out-of-plane B-field, consistent with an in-plane spin-valley field. In principle, this strong Electric dipole spin resonance (EDSR) effect could be utilized for fast all-electrical spin control in small-scale devices.