SurfaceScience21 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 48: Poster Session IV: Surface dynamics II: Phase transitions and elementary processes

O 48.1: Poster

Dienstag, 2. März 2021, 13:30–15:30, P

Ultrafast microscopy of charge density wave phase transitions using pump-probe imaging ellipsometry — •Sebastian Rohrmoser, Tobias Heinrich, Julius B. Peters, Murat Sivis, and Claus Ropers — IV. Physical Institute, Georg-August-University Göttingen, Germany

Null Ellipsometry has a long history of being a powerful, surface sensitive tool for measuring small changes in the refractive index of a sample with a high lateral resolution. These changes may stem from molecular adsorption [1], thin film growth [2] or phase transitions [3]. However, electronic phase transitions between charge density wave (CDW) phases occur on a much shorter timescale and are therefore inaccessible by conventional ellipsometry. Here, we present an all-optical, ultrafast approach to analyzing the phase transition between the nearly commensurate and incommensurate CDW phase in the transition-metal dichalcogenide (TMDC) 1T-TaS2. By combining a null ellipsometer with a pump probe setup, we are able to study the optically driven phase transition with a femtosecond temporal and micrometer lateral resolution. Using heat transfer simulations, we can disentangle the phase transition from the temperature contributions to give better insight in the surface-near dynamics. These results open the pathway for analyzing phase transitions on microstructured surfaces to investigate possible applications of TMDC's as optoelectronic components.

[1] H. Elwing, Elsevier 19, Issues 4-5, 397-406 (1998)

[2] J. Lee et al., Rev. of Scientific Instr. 69, 1800-1810 (1998)

[3] S. Faiss et at., J. Phys. Chem. B, 111, 50, 13979-13986 (2007)