Dresden 2026 – scientific programme
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O: Fachverband Oberflächenphysik
O 38: Ultrafast electron dynamics at surface and interfaces II
O 38.6: Talk
Tuesday, March 10, 2026, 11:45–12:00, TRE/MATH
Lightwave-driven flat bands in a van der Waals crystal — •Changhua Bao1, Vincent Eggers1, Manuel Meierhofer1, Jakob Helml1, Lasse Münster1, Suguru Ito2, Leon Machtl1, Sarah Zajusch2, Giacomo Inzani1, Ludwig Wittmann1, Marlene Liebich1, Robert Wallauer2, Ulrich Höfer1,2, and Rupert Huber1 — 1Department of Physics, University of Regensburg, Regensburg, Germany — 2Department of Physics, Philipps-University of Marburg, Marburg, Germany
Flat bands lead to an extremely high density of states and suppressed kinetic energy, thereby increasing electronic correlations and leading to intriguing light-matter interaction. Here, we reveal the band structure of the van der Waals crystal NbOCl2 using photoelectron momentum microscopy. We directly map out an electronic band that is flat throughout the entire Brillouin zone and well isolated from both the conduction and remote valence bands. By utilizing subcycle photoemission spectroscopy [1,2], the dynamics of the flat band under atomically strong mid-infrared light fields are explored. Intriguingly, the carrier field of light induces long-lived collective modes, which are resolved with subcycle precision. These collective modes not only accelerate the electrons but also renormalize the energy of the flat band. We investigate the microscopic mechanisms of these dynamics, highlighting novel possibilities of flat bands in strong-field physics.
[1] Reimann et al., Nature 562, 396 (2018); [2] Ito et al., Nature 616, 696 (2023)
Keywords: Flat band; Time-resolved momentum microscopy