1. School of Physics and Henan Key Laboratory of Boron Chemistry and Advanced Energy MaterialsHenan Normal University Xinxiang 453007 China
2. Department of Physics and AstronomyUniversity of California Irvine California 92697 USA
3. Department of Mechanical EngineeringUniversity of Michigan Ann Arbor MI 48109 USA
4. Key Laboratory of Polar Materials and Devices (MOE) and Department of OptoelectronicsEast China Normal University Shanghai 200062 China
5. School of Mathematics and PhysicsSuzhou University of Science and Technology Suzhou Jiangsu 215009 China
6. Siyuan LaboratoryGuangdong Provincial Engineering Technology Research Center of Vacuum Coating Technologies and New Energy MaterialsDepartment of PhysicsJinan University Guangzhou 510632 China