1. Chair for Experimental Physics 1, University of Augsburg, Augsburg 86159, Germany
2. School of Physics, University of Western Australia, Crawley 6009, WA, Australia
3. Center for NanoScience (CeNS), Ludwig-Maximilians-Universität Munich, Munich 80799, Germany
4. Augsburg Center for Innovative Technologies (ACIT), Augsburg 86159, Germany