Symmetry-controlled singlet-triplet transition in a double-barrier quantum ring

Heidi Potts,Sebastian Lehmann,Stephanie M Reimann,Josef Josefi,Jakob Bengtsson,Claes Thelander,Kimberly A Dick,I-Ju Chen,Martin Leijnse

doi:10.1103/physrevb.104.l081409

Abstract

We engineer a system of two strongly confined quantum dots to gain reproducible electrostatic control of the spin at zero magnetic field. Coupling the dots in a tight ring-shaped potential with two tunnel barriers, we demonstrate that an electric field can switch the electron ground state between a singlet and a triplet configuration. Comparing our experimental co-tunneling spectroscopy data to a full many-body treatment of interacting electrons in a double-barrier quantum ring, we find excellent agreement in the evolution of many-body states with electric and magnetic fields. The calculations show that the singlet-triplet energy crossover, not found in conventionally coupled quantum dots, is made possible by the ring-shaped geometry of the confining potential.

Highlights

The ability to engineer electron spin states is key for a wide range of applications, from sensing to quantum computation [1,2,3]
Coupling the dots in a tight ring-shaped potential with two tunnel barriers, we demonstrate that an electric field can switch the electron ground state between a singlet and a triplet configuration
While it can be controlled with magnetic fields (Zeeman effect), electrostatic tuning is of interest for fast and selective operations

Summary

Introduction

The ability to engineer electron spin states is key for a wide range of applications, from sensing to quantum computation [1,2,3]. Symmetry-controlled singlet-triplet transition in a double-barrier quantum ring We engineer a system of two strongly confined quantum dots to gain reproducible electrostatic control of the even-electron spin at zero magnetic field.

Results

Conclusion