Dresden 2020 – scientific programme

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MA: Fachverband Magnetismus

MA 48: Ultrafast Electron Dynamics III (joint session O/MA)

MA 48.3: Talk

Thursday, March 19, 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 Bauer¹ — ¹Institute 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).