1. MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter and State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong University Xi'an 710049 China
2. Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province College of Physics and Optoelectronic Engineering Shenzhen University Shenzhen 518060 China
3. Solid State Physics Department of Materials Science and Engineering Ångström Laboratory Uppsala University Box 35 Uppsala 75103 Sweden
4. Department of Electrical and Electronics Engineering Faculty of Engineering The University of Hong Kong Pokfulam Hong Kong