Su-Yang Xu, Madhab Neupane, Chang Liu, Duming Zhang, Anthony Richardella, L. Andrew Wray, Nasser Alidoust, Mats Leandersson, Thiagarajan Balasubramanian, Jaime Sánchez-Barriga, Oliver Rader, Gabriel Landolt, Bartosz Slomski, Jan Hugo Dil, Jürg Osterwalder, Tay-Rong Chang, Horng-Tay Jeng, Hsin Lin, Arun Bansil, Nitin Samarth, M. Zahid Hasan
Understanding and control of spin degrees of freedom on the surfaces of topological materials are key to future applications as well as for realizing novel physics such as the axion electrodynamics associated with time-reversal (TR) symmetry breaking on the surface. We experimentally demonstrate magnetically induced spin reorientation phenomena simultaneous with a Dirac-metal to gapped-insulator transition on the surfaces of manganese-doped Bi2Se3 thin films. The resulting electronic groundstate exhibits unique hedgehog-like spin textures at low energies, which directly demonstrate the mechanics of TR symmetry breaking on the surface. We further show that an insulating gap induced by quantum tunnelling between surfaces exhibits spin texture modulation at low energies but respects TR invariance. These spin phenomena and the control of their Fermi surface geometrical phase first demonstrated in our experiments pave the way for the future realization of many predicted exotic magnetic phenomena of topological origin.
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http://arxiv.org/abs/1212.3382
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