Affiliation: | aService de Physique de l’État Condensé, DSM, CEA-Saclay, F-91191 Gif-sur-Yvette Cedex, France;bSolid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland;cSchool of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, UK |