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HL: Fachverband Halbleiterphysik
HL 25: Poster 2D Materials: Electronic Structure and Exitations (joint session O/HL)
HL 25.2: Poster
Dienstag, 18. März 2025, 13:30–15:30, P3
Influence of surface relaxations on scanning probe microscopy images of the charge density wave material NbSe2 — Nikhil S. Sivakumar1, Joost Aretz1, •Sebastian Scherb1, Marion van Midden Mavric2, Nora Huijgen1, Umut Kamber3, Daniel Wegner1, Alexander A. Khajetoorians1, Malte Rösner1, and Nadine Hauptmann1 — 1IMM, Radboud University, Nijmegen, The Netherlands — 2Jožef Stefan Institute, Ljubljana, Slovenia — 3Joseph Henry Laboratories and Department of Physics, Princeton University, Princeton, USA
Scanning tunneling microscopy (STM) images of the charge density wave (CDW) in 2H-NbSe2 at voltages around the Fermi level lack a contrast inversion expected for a single-band CDW. Recent works have ascribed this to a multiband CDW or the displacement of the surface Se atoms. While STM cannot disentangle geometric and electronic structure variations, non-contact atomic force microscopy (nc-AFM) can provide better characterization of the geometric structure due to its sensitivity to the interaction between the charge densities of tip and surface. We employ distance-dependent combined constant-height STM/nc-AFM measurements to characterize the surface relaxations of 2H-NbSe2. Nc-AFM images show different image contrasts depending on distance. Based on ab-initio calculations, we show that the contrast at small distances is dominated by the displacement of the surface Se atoms. For large distances, the contrast is dominated by the interaction of the permanent dipole of the tip with the potential above the surface that is predominantly modulated by the underlying Nb atoms.
Keywords: CDW; AFM; STM