Dresden 2020 – scientific programme

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O: Fachverband Oberflächenphysik

O 47: Poster Session - 2D Materials: Electronic Structure, Excitations, etc.

O 47.8: Poster

Tuesday, March 17, 2020, 18:15–20:00, P2/EG

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

Transition metal-Dichalcogenides (TMDC's) have long been studied as effectively 2D layered systems exhibiting interesting ordering phenomena such as charge density waves (CDW). A variety of experimental techniques in a pump probe fashion have been used to disentangle the fundamental processes leading to the charge ordering including electron diffraction [1], photoemission spectroscopy [2] and transient optical reflectivity [3]. However, spatiotemporal behaviour like domain growth and movement is not well studied.

In this contribution, we present an all-optical approach to measure the complex refractive index of optically excited 1T-TaS2 on a femtosecond temporal and micrometer spatial scale. Specifically, using a pump probe ellipsometry setup with a rotating polarizer we detect the optically driven phase transition between the nearly commensurate (NC) and incommensurate (IC) CDW phase. The scheme will be applied to study the spatiotemporal dynamics of excited CDW states and phase transitions for inhomogeneous excitations.

[1] M. Eichberger et. al., Nature 468, 799-802 (2010)

[2] J.C. Petersen et.al., Phys. Rev. Lett. 107, 177402 (2011)

[3] N. Dean et.al., Phys. Rev. Lett. 106, 016401 (2011)