Correlating Structural, Electronic, and Magnetic Properties of Epitaxial VSe2 Thin Films

Abstract

The electronic and magnetic properties of transition metal dichalcogenides are known to be extremely sensitive to their structure. In this paper we study the effect of structure on the electronic and magnetic properties of mono- and bilayer $VS{e}_2$ films grown using molecular beam epitaxy. $VS{e}_2$ has recently attracted much attention due to reports of emergent ferromagnetism in the 2D limit. To understand this important compound, high quality 1T and distorted 1T films were grown at temperatures of 200 ${}^{\text{o}}$C and 450 ${}^{\text{o}}$C respectively and studied using 4K Scanning Tunneling Microscopy/Spectroscopy. The measured density of states and the charge density wave (CDW) patterns were compared to band structure and phonon dispersion calculations. Films in the 1T phase reveal different CDW patterns in the first layer compared to the second. Interestingly, we find the second layer of the 1T-film shows a CDW pattern with 4a $\times$ 4a periodicity which is the 2D version of the bulk CDW observed in this compound. Our phonon dispersion calculations confirm the presence of a soft phonon at the correct wavevector that leads to this CDW. In contrast, the first layer of distorted 1T phase films shows a strong stripe feature with varying periodicities, while the second layer displays no observable CDW pattern. Finally, we find that the monolayer 1T $VS{e}_2$ film is weakly ferromagnetic, with ~ $3.5{\mu }_B$ per unit similar to previous reports.

arXiv comment19 pages, 10 figures

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Cited by in corpus (8)

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• On the Nature of Interlayer Bonds in Two-dimensional Materials
• Dimensional crossover and symmetry transformation of the charge density waves in VSe2
• A Quantum Monte Carlo study of the structural, energetic, and magnetic properties of two-dimensional (2D) H and T phase VSe${}_2$
• Atomic arrangement of van der Waals heterostructures using X-ray scattering and crystal truncation rod analysis
• Long-Range Superconducting Proximity Effect in Nickel Nanowires
• Alloying 2D VSe2 with Pt: from a charge density wave state to a disordered insulator
• Enhanced thermopower in two-dimensional ruthenium dichalcogenides $Ru{X}_2$ (X = S, Se): a first-principles study