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O: Fachverband Oberflächenphysik

O 87: 2D Materials IV: Charge Density Waves and Electronic Properties

O 87.3: Vortrag

Donnerstag, 4. April 2019, 15:30–15:45, H25

Atomic-scale and ultrafast melting of a charge density wave — •Mohamad Abdo^1,2,3, Shaoxiang Sheng¹, Moritz Tritschler¹, Steffen rolf-Pissarczyk^2,3, Luigi Malavolti^1,2,3, Gregrory McMurtrie^1,2,3, Max Hänze^1,2,3, Jacob Burgess⁴, and Sebastian Loth^1,2,3 — ¹University of Stuttgart, Stuttgart, Germany — ²Max-Planck-Institut für Struktur und Dynamik der Materie, Hamburg, Germany — ³Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany — ⁴University of Manitoba, Winnipeg, Canada

NbSe2 is a layered transition metal dichalcogenide (TMD) that features CDW phases between 33K and 7K. These phases exhibit collective modes in phase and amplitude. The CDW is disturbed by atomic defects that act as pinning centers [1-2]. Here we use a THz-coupled scanning tunneling microscope (STM) [3] to measure the picosecond dynamic response of the CDW locally at individual atomic defects. Pairs of THz pulses excite the CDW and probe the response in the sample*s density of states with a time resolution better than 200 fs. We find an efficient excitation mechanism driven by the tip-enhanced THz electric field in the STM junction. This excitation melts the CDW by an ultrafast displacement current and triggers a rich dynamical response that varies on the scale of one unit cell of the CDW.

[1] P. Soumyanarayanan, PNAS 110, 1623-1627 (2013). [2] X. Xi, et al. Nature Nanotechnology 10, 765-769 (2015) [3] T. Cocker, et al., Nature Photonics 7, 620-625 (2013).