Intersystem crossing and exciton\u2013defect coupling of spin defects in hexagonal boron nitride

Tyler J Smart,Junqing Xu,Kejun Li,Yuan Ping

doi:10.1038/s41524-021-00525-5

Abstract

Despite the recognition of two-dimensional (2D) systems as emerging and scalable host materials of single-photon emitters or spin qubits, the uncontrolled, and undetermined chemical nature of these quantum defects has been a roadblock to further development. Leveraging the design of extrinsic defects can circumvent these persistent issues and provide an ultimate solution. Here, we established a complete theoretical framework to accurately and systematically design quantum defects in wide-bandgap 2D systems. With this approach, essential static and dynamical properties are equally considered for spin qubit discovery. In particular, many-body interactions such as defect–exciton couplings are vital for describing excited state properties of defects in ultrathin 2D systems. Meanwhile, nonradiative processes such as phonon-assisted decay and intersystem crossing rates require careful evaluation, which competes together with radiative processes. From a thorough screening of defects based on first-principles calculations, we identify promising single-photon emitters such as SiVV and spin qubits such as TiVV and MoVV in hexagonal boron nitride. This work provided a complete first-principles theoretical framework for defect design in 2D materials.

Highlights

Addressable defect-based qubits offer a distinct advantage in their ability to operate with high fidelity under room temperature conditions[1,2]
The spin–orbit contribution to zero-field splitting (ZFS) was computed with the ORCA code. We find that both defects have sizable ZFS including both spin–spin and spin–orbit contributions of 19.4 GHz for TiVV and 5.5 GHz for MoVV, highlighting the potential for the basis of a spin qubit with optically detected magnetic resonance (ODMR)
We found that CVV(T), SiVV(S), SiVV(T), SVV(S), GeVV(S), and SnVV(S) could be promising single-photon emitters (SPEs) defects ((T) denotes triplet; (S) denotes singlet), with a bright intradefect transition and radiative lifetimes on the order of 10 ns, at the same order of magnitude of the SPEs’ lifetime observed experimentally[34]

Summary

Introduction

Addressable defect-based qubits offer a distinct advantage in their ability to operate with high fidelity under room temperature conditions[1,2]. The identification of stable single-photon emitters (SPEs) in 2D materials has opened up a new playground for novel quantum phenomena and quantum technology applications, with improved scalability in device fabrication and leverage in doping spatial control, qubit entanglement, and qubit tuning[3,4]. Persistent challenges must be resolved before 2D quantum defects can become the most promising quantum information platform. These challenges include the undetermined chemical nature of existing SPEs7,11, difficulties in the controlled generation of desired spin defects, and scarcity of reliable theoretical methods which can accurately predict critical physical parameters for defects in 2D materials due to their complex many-body interactions

Methods

Results

Conclusion