SKM 2023 – scientific programme
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O: Fachverband Oberflächenphysik
O 8: Ultrafast Electron Dynamics at Surface and Interfaces I
O 8.7: Talk
Monday, March 27, 2023, 12:00–12:15, TRE Phy
Subcycle surface-bulk coupling in a topological insulator — •Suguru Ito1, Michael Schüler2, Manuel Meierhofer3, Josef Freudenstein3, Dmytro Afanasiev3, Jens Güdde1, Michael Sentef4, Rupert Huber3, and Ulrich Höfer1 — 1Philipps-Universität Marburg, Germany — 2Paul Scherrer Institute, Switzerland — 3Universität Regensburg, Germany — 4Max Planck Institute for the Structure and Dynamics of Matter, Germany
Intense lightwaves at terahertz frequencies can drive currents in electronic bands as well as non-perturbative excitations across the band gap, whose interplay leads to strong-field phenomena such as high-harmonic generation. Angle-resolved photoemission spectroscopy (ARPES) with subcycle time resolution allows us to observe such lightwave-driven processes in momentum space.
Here, we will present our investigation of subcycle coupling between the topological surface state (TSS) and the bulk conduction band (BCB) in Bi2Te3, where the TSS is well seperated from the bulk along the Γ-K direction. Under exposure of a strong 25-THz lightwave, however, transient replicas of the equilibrium TSS, Floquet-Bloch states, are formed. Their hybridization with the BCB enables an efficient population transfer into the BCB. In contrast, TSS and BCB are less separated along Γ-M, where already an intraband current can induce an efficient subcycle population transfer. Both distinct mechanisms are readily seen in our experiment. The dynamical Floquet-bulk coupling is confirmed by our full quantum calculations and provides a momentum-resolved view of non-perturbative interband excitations.