Dresden 2020 – scientific programme
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O: Fachverband Oberflächenphysik
O 8: Ultrafast Electron Dynamics I: Surfaces and Interfaces (joint session O/MA)
O 8.6: Talk
Monday, March 16, 2020, 11:45–12:00, TRE Phy
Ultrafast electron dynamics in black phosphorus studied by time-resolved photoemission momentum microscopy — •Maciej Dendzik1,2, Shuo Dong1, Tommaso Pincelli1, Samuel Beaulieu1, Patrick Xian1, Helene Seiler1, Martin Wolf1, Laurenz Rettig1, and Ralph Ernstorfer1 — 1Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14915 Berlin, Germany — 2KTH Royal Institute of Technology, Electrum 229, 164 40 Kista, Sweden
Black phosphorus (BP) has recently emerged as a promising material due to its highly anisotropic thermal, electronic and optical properties. The high hole mobility together with a band-gap tunable by thickness in the visible to mid-IR range make BP attractive for future applications in opto-electronics. Therefore, detailed information on both the equilibrium and excited-state electronic band structure of BP is of strong interest. Here we present a fs time-resolved study of transient electronic structure of BP in the entire surface Brillouin zone (SBZ) directly imaged with a momentum microscope using a novel setup for XUV time- and angle-resolved photoemission spectroscopy. The measured dispersion is found to be in good agreement with density functional theory calculations. We find that an optical excitation at 800 nm creates a hot-carrier distribution around the SBZ center, which scatters to two other valleys in the conduction band within ca. 15 fs. We further observe a strong linear dichroism in the optical absorption of BP. Interestingly, the inter-valley scattering dynamics are also found to depend on the pump polarization vector direction.