National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093;
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093;
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093;
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093;
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093;
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093;
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093;
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093;
Research Center for Advanced Science and Technology and Institute of Industrial Science, University of Tokyo, Kamaba 4-6-1, Meguro-Ku, Tokyo 153, Japan;
Research Center for Advanced Science and Technology and Institute of Industrial Science, University of Tokyo, Kamaba 4-6-1, Meguro-Ku, Tokyo 153, Japan;