This article has been retracted at the request of the Editor-in-Chief and corresponding author. Please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). Reason: This article went safely through the peer-review process, but it was unfortunately vitiated at the moment of submission by the infringement of three ethical rules, of which the Editor-in-Chief became aware of a complaint lodged by the interested persons only after publication: (1) Missing agreement from other colleagues including supervisor, (2) missing internal check process of the Institute of Physics, and (3) inappropriate indication of the affiliations since most of the results were obtained in the Institute of Physics rather than in the Harbin Institute of Technology. On the other hand, the colleagues mentioned in point (1) do not agree to be added as co-authors in this article. The corresponding author Dr Jie Shu admits his misconduct and apologizes deeply. He sincerely regrets his improper behaviour.