Funding for this research was provided by:
National Natural Science Foundation of China (61674110, 6167204, 11274238)
Received: 1 February 2019
Accepted: 3 April 2019
First Online: 27 April 2019
: XFW is a professor in the School of Physical Science and Technology, Soochow University. He obtained his BSc degree in 1989 from Shanghai Jiaotong University and earned his PhD degree in 1994 at Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science. YSL is a professor in College of Physics and Engineering, Changshu Institute of Technology. LPZ is a professor in the School of Physical Science and Technology, Soochow University.
: The authors declare that they have no competing interests.
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