1. Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
2. Center for Emergent Matter Science, RIKEN, Wako, Saitama 351-0198, Japan
3. Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universitaet Kaiserslautern, 67663 Kaiserslautern, Germany
4. School of Engineering, University of Glasgow, Glasgow G12 8LT, United Kingdom
5. Department of Physics and Energy Science, University of Colorado at Colorado Springs, Colorado Springs, Colorado 80918, USA