title: Liu et al. reply.
authors: School of Physics, Beijing Institute of Technology, Beijing 100081, China.|State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China.
authors: Feng
authors: F
authors: Liu
authors: School of Physics, Beijing Institute of Technology, Beijing 100081, China.|Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors: Cheng-Cheng
authors: CC
authors: Liu
authors: Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors: Kehui
authors: K
authors: Wu
authors: School of Physics, Beijing Institute of Technology, Beijing 100081, China.
authors: Fan
authors: F
authors: Yang
authors: School of Physics, Beijing Institute of Technology, Beijing 100081, China.|Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors: Yugui
authors: Y
authors: Yao