Abstract

Spin defects in wide-band gap semiconductors are promising systems for the realization of quantum bits, or qubits, in solid-state environments. To date, defect qubits have only been realized in materials with strong covalent bonds. Here, we introduce a strain-driven scheme to rationally design defect spins in functional ionic crystals, which may operate as potential qubits. In particular, using a combination of state-of-the-art ab-initio calculations based on hybrid density functional and many-body perturbation theory, we predicted that the negatively charged nitrogen vacancy center in piezoelectric aluminum nitride exhibits spin-triplet ground states under realistic uni- and bi-axial strain conditions; such states may be harnessed for the realization of qubits. The strain-driven strategy adopted here can be readily extended to a wide range of point defects in other wide-band gap semiconductors, paving the way to controlling the spin properties of defects in ionic systems for potential spintronic technologies.

Highlights

  • PBE (a) and formation energy of VN and oxygen impurities (ON) computed within PBE0 (b)

  • We proposed a strain-driven defect design scheme to obtain point defects with localized spin-triplet ground states for implementation of spin qubits in piezoelectric aluminum nitride

  • We found that negatively charged nitrogen vacancies exhibit localized spin-triplet states in n-type aluminum nitride under realistic strain conditions

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Summary

Introduction

The lowest-energy effective spin for a given charge state is shown. The inset of (b) is a schematic representation of the defect-molecule model of VN. The nearest neighbor Al atoms (numbered spheres) around the vacancy site and the Al sp[3] dangling bonds are shown for clarity. The Jahn-Teller distortions for the S = 0 and the S = 1 states are described by the e and a1+ e symmetrized displacements, respectively, as schematically shown next to the defect level diagrams. We found that by applying moderate uni- and bi-axial strain to the host lattice in the presence of negatively charged N vacancies, we could stabilize spin-triplet states, which are well-localized within the fundamental gap of n-type w-AlN.

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