Spin ground state and optical excitations in the vacancy/oxygen defect in the hexagonal BN.
POSTER
Abstract
Chidubem Umeh1, Marisol Alcántara Ortigoza2, and Sergey Stolbov1
1University of Central Florida, Orlando, FL; 2Tuskegee University, Tuskegee Institute AL
The triplet-spin-state local defects in 2D semiconductors are promising spin qubits for quantum computers. In this computational work we focus on the VBON defect in 2D hexagonal BN which combines a B-vacancy and an O-atom substituting a neighboring N. Our calculations confirm the previously reported occurrence of a triplet state in this defect [1]. However, we find that the phonon spectrum of this system has imaginary frequency modes indicating the triplet structure is dynamically unstable. Next, we use the displacement pattern of one of the imaginary modes to distort the VBON structure to facilitate the structural transition expected from the instability. It resulted in the transformation to a dynamically stable singlet state of total energy lower than that of the triplet state. We thus conclude that the stable ground state VBON configuration is a singlet. Our Bethe-Salpeter calculations show that in contrast to the triplet [1], the singlet defect has a sharp optical excitation peak at 2.5 eV that is promising for single-photon-emission applications.
[1] S. Gao, H.-Y. Chen, and M. Bernardi, npj Comput. Mat. 7:85 (2021).
1University of Central Florida, Orlando, FL; 2Tuskegee University, Tuskegee Institute AL
The triplet-spin-state local defects in 2D semiconductors are promising spin qubits for quantum computers. In this computational work we focus on the VBON defect in 2D hexagonal BN which combines a B-vacancy and an O-atom substituting a neighboring N. Our calculations confirm the previously reported occurrence of a triplet state in this defect [1]. However, we find that the phonon spectrum of this system has imaginary frequency modes indicating the triplet structure is dynamically unstable. Next, we use the displacement pattern of one of the imaginary modes to distort the VBON structure to facilitate the structural transition expected from the instability. It resulted in the transformation to a dynamically stable singlet state of total energy lower than that of the triplet state. We thus conclude that the stable ground state VBON configuration is a singlet. Our Bethe-Salpeter calculations show that in contrast to the triplet [1], the singlet defect has a sharp optical excitation peak at 2.5 eV that is promising for single-photon-emission applications.
[1] S. Gao, H.-Y. Chen, and M. Bernardi, npj Comput. Mat. 7:85 (2021).
Presenters
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Chidubem Umeh
University of Central Florida
Authors
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Chidubem Umeh
University of Central Florida