1. Department of Materials Science and Engineering Southern University of Science and Technology Shenzhen 518055 P. R. China
2. Department of Physics The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong 999077 P. R. China
3. Center for Phononics and Thermal Energy Science School of Physics Science and Engineering Institute for Advanced Study Tongji University Shanghai 200092 P. R. China
4. Wuhan National Laboratory for Optoelectronics (WNLO) and the School of Optical and Electronic Information Huazhong University of Science and Technology Wuhan 430074 P. R. China
5. Guangdong Provincial Key Laboratory of Energy Materials for Electric Power Shenzhen 518055 P. R. China