[1] Johannes Gutenberg Univ Mainz, Inst Phys, D-55128 Mainz, Germany
[2] Univ Paris Saclay, Univ Paris Sud, CNRS, Unite Mixte Phys,Thales, F-91767 Palaiseau, France
[3] Grad Sch Excellence Mat Sci Mainz, Staudinger Weg 7, D-55128 Mainz, Germany
[4] Univ Glasgow, Elect & Nanoscale Engn Div, James Watt Sch Engn, Glasgow G12 8QQ, Lanark, Scotland