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TT: Fachverband Tiefe Temperaturen

TT 65: Topological Insulators I (joint session DS, HL, MA, O, TT, organized by HL)

TT 65.7: Talk

Thursday, March 23, 2017, 11:45–12:00, POT 251

Ultrafast mid-IR pump, THz probe spectroscopy investigating of the topological insulator BSTS — •Matteo Montagnese, Jingy Zhu, Chris Rheinhoffer, Yoichi Ando, and Paul H. M. van Loosdrecht — II. Physikalishes Institut der Universität zu Köln, Zülpicher str 77, D-25127 Köln

We present ultrafast pump-probe measurements on the topological insulator BSTS. We employed a high-intensity tunable mid-IR pulse (2-10 microns) as a pump, generated by difference-frequency mixing in an optical parametric amplifier to excite the BSTS system below the onset of the bulk optical electronic continuum. Upon excitation, the far-IR (0.1-3 THz) response of the system has been probed by a single-cycle coherent THz pulse, generated by optical rectification of a near-IR pulse. The time-resolved transmittance of the THz spectra have been measured employing optical sampling and time-domain techniques. By tuning the pump energy, the impurity states leading to charge puddle formation and the surface state are selectively populated, with the aim of disentangling their respective contributions to the dynamic optical conductivity.