School of Science Wuhan Textile University Wuhan 430073 China;
Key Lab of Information Materials of Sichuan Province South-west University for Nationalities Chengdu 610041 China;
Lab for Low-dimensional Structure Physics Institute of Solid State Physics and School of Physics and Electronic Engineering Sichuan Normal University Chengdu 610068 China;
Lab for Low-dimensional Structure Physics Institute of Solid State Physics and School of Physics and Electronic Engineering Sichuan Normal University Chengdu 610068 China;
