Ni, G. X.
Wang, H.
Wu, J. S.
Fei, Z.
Goldflam, M. D.
Keilmann, F.
Özyilmaz, B.
Castro Neto, A. H.
Xie, X. M.
Fogler, M. M.
Basov, D. N.
Article History
Received: 6 April 2015
Accepted: 17 August 2015
First Online: 28 September 2015
Competing interests
: F.K. is one of the co-founders of Neaspec, producer of the s-SNOM apparatus used in this study.