Affiliation: | Department of Applied Physics, University of Tianjin, Tianjin 300072, China Department of Applied Physics, University of Tianjin, Tianjin 300072, China Department of Applied Physics, University of Tianjin, Tianjin 300072, China Department of Applied Physics, University of Tianjin, Tianjin 300072, China Department of Applied Physics, University of Tianjin, Tianjin 300072, China |