Spin reorientation transition on the surface of a topological insulator

Su-Yang Xu, M. Neupane, Chang Liu, D. M. Zhang, A. Richardella, L. A. Wray, 3 N. Alidoust, M. Leandersson, T. Balasubramanian, J. Sanchez-Barriga, O. Rader, G. Landolt, 7 B. Slomski, 7 J. H. Dil, 7 T.-R. Chang, H.-T. Jeng, 8 J. Osterwalder, H. Lin, A. Bansil, N. Samarth, and M. Z. Hasan Joseph Henry Laboratory, Department of Physics, Princeton University, Princeton, New Jersey 08544, USA Department of Physics, Penn State University, University Park, PA 16802 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94305, USA MAX-lab, P.O. Box 118, S-22100 Lund, Sweden Helmholtz-Zentrum Berlin fur Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Str. 15, D-12489 Berlin, Germany Swiss Light Source, Paul Scherrer Institute, CH-5232, Villigen, Switzerland Physik-Institute, Universitat Zurich-Irchel, CH-8057 Zurich, Switzerland Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan Institute of Physics, Academia Sinica, Taipei 11529, Taiwan Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA