Berlin 2018 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 116: Focus Session: Structural Dynamics in Nanoscale Materials, Probed by Ultrafast Electron Pulses III
O 116.6: Vortrag
Freitag, 16. März 2018, 12:00–12:15, HE 101
Femtosecond Electron Dynamics at the Single Atom Level — •Mohamad Abdo1,2,3, Steffen Rolf-Pissarczyk2,3, Björn Schlie1,2,3, Luigi Malavolti1,2,3, Jacob Burgess3,4 und Sebastian Loth1,2,3 — 1Universität Stuttgart, Institut für Funktionelle Materie und Quantentechnologien, Stuttgart, Germany — 2Max-Planck-Institut für Struktur und Dynamik der Materie, Hamburg, Germany — 3Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany — 4Department of Physics and Astronomy, University of Manitoba, Winnipeg, Canada
Layered transition metal dichalcogenides (TMD) have complex electronic structure. Some of them as NbSe2 and TaS2, feature charge density wave (CDW) phases in which the electrons order with a periodicity that is incommensurate with the atomic lattice. Studies using optical pump probe techniques showed a picosecond response of the CDW [1] as well as a strong impact of pinning to atomic-sized defects [2]. Here we apply THz-coupled scanning tunneling microscopy [3] to measure the ultrafast dynamics of a 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 that the CDW responds to an excitation on a timescale well below 1ps and exhibits rich dynamics with a string spatial variation on the scale of one unit cell of the CDW. [1] X. Xi, et al. Nature Nanotechnology 10, 765-769 (2015) [2] P. Soumyanarayanan, PNAS 110, 1623-1627 (2013). [3] T. Cocker, et al., Nature Photonics 7, 620-625 (2013).