Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 36: Poster III

HL 36.33: Poster

Wednesday, March 20, 2024, 18:00–20:30, Poster E

Coherent interlayer phonons in van der Waals MoSe2/WSe2 heterobilayers — Changxiu Li^{1, 2}, Alexey V. Scherbakov¹, •Pedro Soubelet³, Anton K. Samusev¹, Claudia Ruppert¹, Nilanthy Balakrishnan⁴, Vitalyi E. Gusev², Andreas V. Stier³, Jonathan J. Finley³, Manfred Bayer¹, and Andrey V. Akimov⁵ — ¹Experimentelle Physik 2, Technische Universität Dortmund, Germany. — ²Laboratoire d'Acoustique de l'Université du Mans, Institut d'Acoustique-Graduate School, Le Mans Université, France. — ³Walter Schottky Institut and TUM School of Natural Sciences, Technische Universität München, Germany. — ⁴School of Chemical and Physical Sciences, Keele University, United Kingdom. — ⁵School of Physics and Astronomy, University of Nottingham, United Kingdom.

The increasing role of two-dimensional (2D) devices requires the development of new techniques for ultrafast control. A special feature of heterobilayers (HBs) assembled from van der Waals (vdW) monolayers is the femtosecond separation of photoexcited electrons and holes between the neighboring layers, resulting in the formation of Coulomb forces. Using laser pulses, we generate a 0.8THz coherent breathing mode in MoSe2/WSe2 HBs, which modulates the thickness of the HB and should modulate the photogenerated electric field in the vdW gap. While the phonon frequency and decay time are independent of the stacking angle between monolayers, the amplitude decreases at intermediate angles, which is explained by a decrease in the photogenerated electric field between the layers.

Keywords: Coherent phonons; Van der Waals heterostructures; Interlayer excitons; THz radiation; Pump-probe spectroscopy