Regensburg 2019 – wissenschaftliches Programm
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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 Abdo1,2,3, Shaoxiang Sheng1, Moritz Tritschler1, Steffen rolf-Pissarczyk2,3, Luigi Malavolti1,2,3, Gregrory McMurtrie1,2,3, Max Hänze1,2,3, Jacob Burgess4, and Sebastian Loth1,2,3 — 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).