Nonlinear electronic polarization and optical response in borophosphate BPO4

作者：Li, Zhi; Liu, Qiong; Han, Shujuan; Iitaka, Toshiaki; Su, Haibin; Tohyama, Takami; Jiang, Huaidong; Dong, Yongjun; Yang, Bin; Zhang, Fangfang; Yang, Zhihua^*; Pan, Shilie

来源：Physical Review B, 2016, 93(24): 245125.

DOI：10.1103/PhysRevB.93.245125

• SEMICONDUCTORS

The electronic structure, nonlinear electronic polarization induced by a static external electric field, and frequency dependent second-harmonic susceptibility tensor of the borophosphate BPO4 are studied by a first-principles calculation based on density-functional theory. Our calculated results show that the borophosphate BPO4 has a large band gap similar to 10.4 eV, which is larger than the band gap of the widely used nonlinear optical crystal KBe2BO3F2. However, BPO4 also has a nonlinear coefficient d(36) = 0.92 pm/V at static limit, which also is larger than the nonlinear coefficient d(11) = 0.47 pm/V of KBe2BO3F2. The unexpected larger nonlinear coefficient of BPO4 can be interpreted by the relatively strong s-p hybridization in BPO4, which can enhance the inter-band Berry connections, while the O 2p orbitals dominating valence bands in KBe2BO3F2 are very flat, resulting from weak s-p hybridization.

• 单位
  中国科学院上海光学精密机械研究所; 哈尔滨工业大学; 中国科学院新疆理化技术研究所; 山东大学; 晶体材料国家重点实验室; 中国科学院大学