Electrical control of spins and giant g-factors in ring-like coupled quantum dots

H Potts,M Nilsson,S Lehmann,M Leijnse,A Tsintzis,I.–J Chen,C Thelander,K A Dick

doi:10.1038/s41467-019-13583-7

Abstract

Emerging theoretical concepts for quantum technologies have driven a continuous search for structures where a quantum state, such as spin, can be manipulated efficiently. Central to many concepts is the ability to control a system by electric and magnetic fields, relying on strong spin-orbit interaction and a large g-factor. Here, we present a mechanism for spin and orbital manipulation using small electric and magnetic fields. By hybridizing specific quantum dot states at two points inside InAs nanowires, nearly perfect quantum rings form. Large and highly anisotropic effective g-factors are observed, explained by a strong orbital contribution. Importantly, we find that the orbital contributions can be efficiently quenched by simply detuning the individual quantum dot levels with an electric field. In this way, we demonstrate not only control of the effective g-factor from 80 to almost 0 for the same charge state, but also electrostatic change of the ground state spin.

Highlights

Emerging theoretical concepts for quantum technologies have driven a continuous search for structures where a quantum state, such as spin, can be manipulated efficiently
quantum dots (QDs) made from carbon nanotubes were found to have a very different electronic structure compared to conventional QDs, with a nearly fourfold orbital- and spindegeneracy, broken by spin-orbit interaction[7,9,10], and anisotropic effective g-factors (g*) resulting from the orbital contributions[5]
The quantum rings studied in this work appear inside quantum wells (QWs) formed during epitaxial growth of InAs nanowires[21]

Summary

Introduction

Emerging theoretical concepts for quantum technologies have driven a continuous search for structures where a quantum state, such as spin, can be manipulated efficiently. The four states at B = 0 are split by the spin-orbit interaction energy (ΔSOI) into two pairs, similar to the Kramers doublets (K↓, K’↑) and (K↑, K’↓) for carbon nanotubes.

Results

Conclusion