ADAQ-SYM: Automated symmetry analysis of defect orbitals

Quantum technologies like single photon emitters and qubits can be enabled by point defects in semiconductors, with the NV-center in diamond being the most prominent example. There are many different semiconductors, each potentially hosting interesting defects. The symmetry properties of the point defect orbitals can yield useful information about the behavior of the system, such as the interaction with polarized light. We have developed a tool to perform symmetry analysis of point defect orbitals obtained by plane-wave density functional theory simulations. The software tool, named ADAQ-SYM, calculates the characters for each orbital, finds the irreducible representations, and uses selection rules to find which optical transitions are allowed. The capabilities of ADAQ-SYM are demonstrated on several defects in diamond and 4H-SiC. The symmetry analysis explains the different zero phonon line (ZPL) polarization of the hk and kh divacancies in 4H-SiC.诸如单光子发射器与量子比特（qubit）之类的量子技术，可依托半导体中的点缺陷得以实现，其中金刚石中的氮-空位中心（NV-center）便是最具代表性的范例。半导体种类繁多，每一类都有可能承载具有研究价值的缺陷。点缺陷轨道的对称性特性，可提供该体系行为的关键信息，例如其与偏振光的相互作用规律。我们开发了一款工具，用于对通过平面波密度泛函理论（plane-wave density functional theory）模拟得到的点缺陷轨道开展对称性分析。这款名为ADAQ-SYM的软件工具，可计算每个轨道的特征标，确定其不可约表示（irreducible representation），并依据选择定则（selection rules）判定允许发生的光学跃迁。我们通过金刚石与4H-SiC中的多种缺陷，验证了ADAQ-SYM的功能性能。该对称性分析可解释4H-SiC中hk与kh双空位的零声子线（zero phonon line, ZPL）偏振特性差异。