Dresden 2020 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 104: Ultrafast Electron Dynamics III (joint session O/MA)

O 104.3: Vortrag

Donnerstag, 19. März 2020, 11:00–11:15, WIL B321

Mode-resolved reciprocal space mapping of electron-phonon interaction in the Weyl semimetal candidate Td-WTe2 — •Petra Hein1, Stephan Jauernik1, Hermann Erk1, Lexian Yang2, Yanpeng Qi3, Yan Sun4, Claudia Felser4, and Michael Bauer11Institute of Experimental and Applied Physics, CAU Kiel, Germany — 2State Key Laboratory of Low Dimensional Quantum Physics, Tsinghua University, China — 3School of Physical Science and Technology, ShanghaiTech University, China — 4Max Planck Institute for Chemical Physics of Solids, Dresden, Germany

The selective excitation of coherent phonons provides unique capabilities to control fundamental properties of quantum materials on ultrafast time scales. For instance, in the presence of strong electron-phonon coupling, the electronic band structure can become substantially modulated. Recently, it was predicted that by this means even topologically protected states of matter can be manipulated: Pairs of Weyl points in Td-WTe2 are expected to annihilate as an interlayer shear mode drives the material towards a centrosymmetric phase [1].
Here, time- and angle-resolved photoelectron spectroscopy is used to monitor the changes in the electronic structure of Td-WTe2 upon absorption of 1.5 eV femtosecond laser pulses. We provide direct experimental evidence that the coherent excitation of the shear mode acts on the electronic states near the Weyl points. By comparison with higher-frequency coherent phonon modes, we finally prove the shear mode-selectivity of the observed changes in the electronic structure.
[1] E. J. Sie et al., Nature 565, 61-66 (2019).

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