1. School of Electronic Science and Engineering, Nanjing University 1 , Nanjing 210023, China
2. National Key Laboratory of Spintronics, Nanjing University 2 , Suzhou 215163, China
3. School of Integrated Circuits, Guangdong University of Technology 3 , Guangzhou 510006, China
4. School of Physics and Engineering, Henan University of Science and Technology 4 , Luoyang 471023, China