Ultrafast Dynamics of Interface Currents

Summary

For many existing electronic devices based on thin films and even more so for novel device concepts based on interface electronic states, the charge transfer parallel to the interface plays a crucial role. Within the framework of this project, we apply experi­mental techniques originally developed for the study of surface currents to investigate lateral electrical currents at internal interfaces in a contact-free fashion and with femtosecond time resolution.

The interface currents are either be excited optically by means of coherent control schemes or by accelerating the electrons with the electric field of strong THz transients. The observation of the current dynamics by time- and angle-resolved photoemission spectroscopy (tr-ARPES) in the full two-dimensional k-space allows us to study the effect of inelastic and elastic momentum scattering at the interface on current transport. We extend previous work on Dirac currents of topological insulators and embed the topological surface state under thin protecting layers for device applications. In parallel, we investigate the effect of interfaces on the decay of photocurrents induced in graphene and graphene-related materials as well as in two dimensional semiconductors such as GaS and InSe.

Project-related publications

1. C.P. Schmid, L. Weigl, P. Grössing, V. Junk, C. Gorini, S. Schlauderer, S. Ito, M. Meierhofer, N. Hofmann, D. Afanasiev, J. Crewse, K.A. Kokh, O.E. Tereshchenko, J. Güdde, F. Evers, J. Wilhelm, K. Richter, U. Höfer, R. Huber
   Tuneable non-integer high-harmonic generation in a topological insulator
   Nature 593 (2021) 385.
2. J. Güdde. U. Höfer
   Ultrafast dynamics of photocurrents in surface states of topological insulators
   Phys. Stat. Sol. B 257 (2020), – Feature Article.
3. K. Sumida, M. Kakoki, J. Reimann, M. Nurmamat, S. Goto, Y. Takeda, Y. Saitoh, K.A. Kokh, O. E. Tereshchenko, J. Güdde, U. Höfer, A. Kimura
   Magnetic-impurity-induced modifications to ultrafast carrier dynamics in the ferromagnetic topological insulators Sb_2-xV_xTe₃
   New J. Phys. 21, 1376 (2019).
4. J. Reimann, S. Schlauderer, C.P. Schmid, F. Langer, S. Baierl, K.A. Kokh, O.E. Tereshchenko, A. Kimura, C. Lange, J. Güdde, U. Höfer, R. Huber
   Subcycle observation of lightwave-driven Dirac currents in a topological surface band
   Nature 562, 396 (2018).
5. K. Kuroda, J. Reimann, K.A. Kokh, O.E. Tereshchenko, A. Kimura, J. Güdde, U. Höfer
   Ultrafast energy- and momentum-resolved surface Dirac photocurrents in the topological insulator Sb₂Te₃
   Phys. Rev. B 95, 081103(R) (2017).