Electrically tunable effective g-factor of a single hole in a lateral GaAs/AlGaAs quantum dot

Sergei Studenikin,Louis Gaudreau,Lisa Tracy,Terry Hargett,Yoshiro Hirayama,D Guy Austing,Motoi Takahashi,Piotr Zawadzki,John Reno,Aviv Padawer-Blatt,Jordan Ducatel,Alex Bogan,Andrew Sachrajda,Marek Korkusinski

doi:10.1038/s42005-019-0262-1

Abstract

Electrical tunability of the g-factor of a confined spin is a long-time goal of the spin qubit field. Here we utilize the electric dipole spin resonance (EDSR) to demonstrate it in a gated GaAs double-dot device confining a hole. This tunability is a consequence of the strong spin-orbit interaction (SOI) in the GaAs valence band. The SOI enables a spin-flip interdot tunneling, which, in combination with the simple spin-conserving charge transport leads to the formation of tunable hybrid spin-orbit molecular states. EDSR is used to demonstrate that the gap separating the two lowest energy states changes its character from a charge-like to a spin-like excitation as a function of interdot detuning or magnetic field. In the spin-like regime, the gap can be characterized by the effective g-factor, which differs from the bulk value owing to spin-charge hybridization, and can be tuned smoothly and sensitively by gate voltages.

Highlights

Electrical tunability of the g-factor of a confined spin is a long-time goal of the spin qubit field
The electric dipole spin resonance (EDSR) frequency is defined by the Zeeman energy EZ, which is set by the static external magnetic field
The strong coupling results in a curved single-hole charge addition line, as well as an extended transport region along this line. This is in contrast to the weak interdot tunneling case, in which the transport signature consists typically only of a so-called triple point, occurring at gate voltages corresponding to the exact energy resonance of the single-hole levels of individual dots

Summary

Introduction

Electrical tunability of the g-factor of a confined spin is a long-time goal of the spin qubit field. We utilize the electric dipole spin resonance (EDSR) to demonstrate it in a gated GaAs double-dot device confining a hole. This tunability is a consequence of the strong spin-orbit interaction (SOI) in the GaAs valence band. The SOI in devices confining electrons is too weak to renormalize the Zeeman gap noticeably This is why local electrostatic tuning of the g-factor for electrons has been attempted by other methods, e.g., by engineering of materials with composition gradients[26,27], exploiting interactions with magnetic impurities[28] or nuclear spins[29], or utilizing a combination of SOI and the Stark shift[30]. In silicon and germanium devices confining holes, weak SOI permits only a small degree of electrical control of the g-factor via engineering of valence subband mixing[17]

Methods

Results

Conclusion