Affiliation: | (1) Drittes Physikalisches Institut, Universit?t G?ttingen, Friedrich-Hund-Platz 1, 37077 G?ttingen, Germany;(2) Universit?t G?ttingen, Friedrich-Hund-Platz 1, 37077 G?ttingen, Germany;(3) Center for Nanoscale Science and Engineering, Department of Mechanical Engineering, North Dakota State University, 111 Dolve Hall, 58105-5285 Fargo, ND, USA |