Local vibrational modes of Si vacancy spin qubits in SiC
Local vibrational modes of Si vacancy spin qubits in SiC
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DOI：
10.1103/physrevb.101.144109
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发表时间：
2020-02
影响因子：
3.7
通讯作者：
Z. Shang;A. Hashemi;Y. Berencén;H. Komsa;P. Erhart;S. Zhou;M. Helm;A. Krasheninnikov;G. Astakhov
中科院分区：
文献类型：
--
作者：
Z. Shang;A. Hashemi;Y. Berencén;H. Komsa;P. Erhart;S. Zhou;M. Helm;A. Krasheninnikov;G. Astakhov
碳化硅是一个非常有前途的量子应用平台，因为在这种技术友好的材料中，点缺陷具有非凡的自旋和光学特性。这些性质受到晶体振动的强烈影响，但它们与自旋量子位行为之间的确切关系尚未得到充分研究。我们揭示了在生长的4H-SiC中Si空位自旋量子比特的局部振动模式。我们应用微波辅助光谱学分离了一种特殊类型的缺陷，即所谓的V2中心，并观察了零声子线以及七个相等分离的声子复制品。此外，我们提出了光致发光线形状的第一性原理计算，与我们的实验数据非常吻合。为了提高计算精度和减少计算时间，我们使用机器学习算法提取力常数。这使我们能够在硅空位的光学发射过程中识别与激发电子耦合的晶格振动的主导模式。共振声子能量为36mev，德拜-沃勒系数约为6%。实验证明，光诱导自旋极化的活化能由局部振动能给出。我们的研究结果深入了解了SiC自旋量子比特中电子态与振动模式的耦合，这对于预测其自旋、光学、机械和热性能至关重要。所描述的方法可以应用于SiC以及其他三维和二维材料中具有光谱重叠贡献的各种自旋缺陷。
Silicon carbide is a very promising platform for quantum applications because of the extraordinary spin and optical properties of point defects in this technologically friendly material. These properties are strongly influenced by crystal vibrations, but the exact relationship between them and the behavior of spin qubits is not fully investigated. We uncover the local vibrational modes of the Si vacancy spin qubits in as-grown 4H-SiC. We apply microwave-assisted spectroscopy to isolate the contribution from one particular type of defects, the so-called V2 center, and observe the zero-phonon line together with seven equally separated phonon replicas. Furthermore, we present first-principles calculations of the photoluminescence line shape, which are in excellent agreement with our experimental data. To boost up the calculation accuracy and decrease the computation time, we extract the force constants using machine-learning algorithms. This allows us to identify the dominant modes in the lattice vibrations coupled to an excited electron during optical emission in the Si vacancy. A resonance phonon energy of 36 meV and a Debye-Waller factor of about 6% are obtained. We establish experimentally that the activation energy of the optically induced spin polarization is given by the local vibrational energy. Our findings give insight into the coupling of electronic states to vibrational modes in SiC spin qubits, which is essential to predict their spin, optical, mechanical, and thermal properties. The approach described can be applied to a large variety of spin defects with spectrally overlapped contributions in SiC as well as in other three-and two-dimensional materials.