Influence of surface relaxations on scanning probe microscopy images of the charge density wave material 2H-NbSe${}_2$

Abstract

Scanning tunneling microscopy is the method of choice for characterizing charge density waves by imaging the variation in atomic-scale contrast of the surface. Due to the measurement principle of scanning tunneling microscopy, the electronic and lattice degrees of freedom are convoluted, making it difficult to disentangle a structural displacement from spatial variations in the electronic structure. In this work, we characterize the influence of the displacement of the surface-terminating Se atoms on the 3 x 3 charge density wave contrast in scanning probe microscopy images of 2H-NbSe${}_2$. In scanning tunneling microscopy images, we observe the 3 x 3 charge density wave superstructure and atomic lattice at all probed tip-sample distances. In contrast, non-contact atomic force microscopy images show both periodicities only at small tip-sample distances while, unexpectedly, a 3 x 3 superstructure is present at larger tip-sample distances. Using density functional theory calculations, we qualitatively reproduce the experimental findings and indicate that the 3 x 3 superstructure at different tip-sample distances in non-contact atomic force microscopy images is a result from different underlying interactions. In addition, we show that the displacement of the surface-terminating Se atoms has a negligible influence to the contrast in scanning tunneling microscopy images. Our combined experimental and theoretic work presents a method on how to discriminate the influence of the surface corrugation from the variation of the charge density to the charge density wave contrast in scanning probe microscopy images, which can provide insights into the influence of structural disorder to a charge density wave ground state.

References in corpus (23)

• Strongly enhanced charge-density-wave order in monolayer NbSe${}_2$
• Characterization of collective ground states in single-layer NbSe2
• Fermi surface nesting and the origin of Charge Density Waves in metals
• Extended Phonon Collapse and the Origin of the Charge-Density-Wave in NbSe${}_2$
• Fermi Surface Nesting and the Origin of the Charge Density Wave in NbSe${}_2$
• Effect of dimensionality on the charge-density-wave in few-layers 2H-NbSe${}_2$
• Two energy gaps and Fermi surface 'arcs' in NbSe2
• Large spin-orbit splitting of deep in-gap defect states of engineered sulfur vacancies in monolayer WS2
• Quasi-Particle Spectra, Charge-Density-Wave, Superconductivity and Electron-Phonon Coupling in 2H-NbSe2
• A quantum phase transition from triangular to stripe charge order in NbSe${}_2$
• How Substitutional Point Defects in Two-Dimensional WS${}_2$ Induce Charge Localization, Spin-Orbit Splitting, and Strain
• Using controlled disorder to probe the interplay between charge order and superconductivity in NbSe2
• Charge Order from Orbital-dependent Coupling Evidenced by NbSe${}_2$
• Quasiparticle Interference, quasiparticle interactions and the origin of the charge density-wave in 2H-NbSe${}_2$
• Electron-phonon coupling and the Coexistence of Superconductivity and Charge-Density Wave in Monolayer NbSe2
• Atomic-Scale Strain Manipulation of a Charge Density Wave
• Microscopic evidence for strong periodic lattice distortion in 2D charge-density wave systems
• Topological Landscape of Competing Charge Density Waves in 2H-NbSe2
• Three-dimensional Fermi surface of 2H-NbSe${}_2$ - Implications for the mechanism of charge density waves
• Experimental evidence for a Bragg glass density wave phase in a transition-metal dichalcogenide
• Revealing the correlation between real-space structure and chiral magnetic order at the atomic scale
• Visualization of alternating triangular domains of charge density waves in 2H-NbSe${}_2$ by scanning tunneling microscopy
• Inelastic electron tunneling in 2H-Ta${}_x$Nb${}_{1-x}$Se${}_2$ evidenced by scanning tunneling spectroscopy