Dresden 2026 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 8: Ultra-fast Phenomena I
HL 8.2: Vortrag
Montag, 9. März 2026, 15:15–15:30, POT/0006
Light-Induced Polarization Switching in R-Stacked Bilayer WSe2 — •Xiangzhou Zhu, Stefono Mocatti, and Matteo Calandra — Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo, Italy
Sliding ferroelectricity in two-dimensional van der Waals materials enables polarization control by relative layer motion, offering a promising platform for novel memory devices. Recent works show that strong laser pulses can reverse the polarization of such systems by driving shear phonons, but the required interlayer sliding and structural distortions limit the achievable switching speed. Here, we demonstrate a purely electronic pathway for light-induced polarization reversal in rhombohedrally stacked bilayer transition-metal dichalcogenides (TMDs). With constrained density-functional theory (cDFT), we find that photoexcited carrier densities below 0.2 e per unit cell are sufficient to switch the intrinsic ferroelectric dipole without interlayer sliding in WSe2. This occurs because photoexcitation induces an imbalanced charge redistribution between the layers, which generates a counter-dipole. Using real-time semiconductor Bloch equation simulations, we shows that the total polarization can reverse by light within a few hundred femtoseconds. Furthermore, time-dependent charge analysis reveals that this ultrafast switching is primarily driven by a localized dipole rearrangement around the tungsten sites. These results establish a new mechanism for electronic control in 2D ferroelectrics, relevant for high-speed volatile memory applications.
Funded by the European Union (ERC, DELIGHT, 101052708)
Keywords: First-principles; Light-induced polarization switching; Constrained density-functional theory; two-dimensional van der Waals materials; Sliding ferroelectrics