Presenter: Prof.Ulrich Hoefer（Department of Physics, Philipps-University of Marburg, Germany）
Topic: Band Structure Movies of Electrical Surface Currents
Time: 10:00AM, June.17th (Monday)
Location: Conference Room B, BLDG 909-1F
Time-resolved photoelectron spectroscopy combines femtosecond pump-probe techniques with angle-resolved photoelectron spectroscopy (ARPES). I will show how this method can be used to perform measurements of electron transport at surfaces and interfaces in a contact-free fashion and with femtosecond time-resolution [1-3]. As the main example, I will discuss Dirac surface states of topological insulators. We induce electrical currents in these states with strong THz transients and directly access their dynamics in momentum space with subcycle time resolution. As a result of spin-momentum locking, the accelerated spin-polarized electrons reach ballistic mean free paths of several hundreds of nanometers. Our results show that topological insulators are promising materials for future lightwave-driven electronics operating at THz clock rates .
 J. Güdde, M. Rohleder, T. Meier, S. W. Koch, and U. H?fer, Science 318, 1287 (2007).
 K. Kuroda, J. Reimann, J. Güdde, and U. H?fer, Phys. Rev. Lett. 116, 076801 (2016).
 J. Reimann, S. Schlauderer, C. P. Schmid, F. Langer, S. Baierl, K. A. Kokh, O. E. Tereshchenko, A. Kimura, C. Lange, J. Güdde, U. H?fer, and R. Huber, Nature 562, 396 (2018).
Contact: Prof. Steffen Duhm