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Momentum-Resolved Spin Dynamics of Bulk and Surface Excited States in the Topological Insulator Bi2Se3

Citace:
CACHO, C., CREPALDI, A., BATTIATO, M., BRAUN, J., CILENTO, F., ZACCHIGNA, M., RICHTER, M., HECKMANN, O., SPRINGATE, E., LIU, Y., DHESI, S., BERGER, H., BUGNON, P., HELD, K., GRIONI, M., EBERT, H., HRICOVINI, K., MINÁR, J., PARMIGIANI, F. Momentum-Resolved Spin Dynamics of Bulk and Surface Excited States in the Topological Insulator Bi2Se3. Physical Review Letters, 2015, roč. 114, č. 9, s. \´097401-1\´- \´097401-5\´. ISSN: 0031-9007
Druh: ČLÁNEK
Jazyk publikace: eng
Anglický název: Momentum-Resolved Spin Dynamics of Bulk and Surface Excited States in the Topological Insulator Bi2Se3
Rok vydání: 2015
Autoři: C. Cacho , A. Crepaldi , M. Battiato , J. Braun , F. Cilento , M. Zacchigna , M.C. Richter , O. Heckmann , E. Springate , Y. Liu , S.S. Dhesi , H. Berger , Ph. Bugnon , K. Held , M. Grioni , H. Ebert , K. Hricovini , Doc.Dr. Jan Minár , F. Parmigiani
Abstrakt EN: The prospect of optically inducing and controlling a spin-polarized current in spintronic devices has generated wide interest in the out-of-equilibrium electronic and spin structure of topological insulators. In this Letter we show that only measuring the spin intensity signal over several orders of magnitude by spin-, time-, and angle-resolved photoemission spectroscopy can provide a comprehensive description of the optically excited electronic states in Bi2Se3 . Our experiments reveal the existence of a surface resonance state in the second bulk band gap that is benchmarked by fully relativistic ab initio spin-resolved photoemission calculations. We propose that the newly reported state plays a major role in the ultrafast dynamics of the system, acting as a bottleneck for the interaction between the topologically protected surface state and the bulk conduction band. In fact, the spin-polarization dynamics in momentum space show that these states display macroscopically different temperatures and, more importantly, different cooling rates over several picoseconds.
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