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O: Fachverband Oberflächenphysik
O 66: Poster Session V: 2D Materials: Electronic structure, excitations, etc. I
O 66.3: Poster
Wednesday, March 3, 2021, 10:30–12:30, P
A full gap above the Fermi level: the charge density wave of monolayer VS2 — •Camiel van Efferen1, Jan Berges2, Joshua Hall1, Erik van Loon2, Stefan Kraus1, Arne Schobert2, Tobias Wekking1, Felix Huttmann1, Eline Plaar1, Nico Rothenbach3, Katharina Ollefs3, Lucas Machado Arruda4, Nick Brookes5, Gunnar Schönhoff2, Kurt Kummer5, Heiko Wende3, Tim Wehling2, and Thomas Michely1 — 1UzK, Köln, Germany — 2UB, Bremen, Germany — 3UDE, Duisburg, Germany — 4FUB, Berlin, Germany — 5ESRF, Grenoble, France
We present experimental evidence, via scanning tunneling microscopy and spectroscopy, of a 2/3ΓK charge density wave (CDW) in monolayer VS2. The CDW is shown to be stable at room temperature, and causes a full CDW gap in the unoccupied states of VS2. Unlike conventional CDWs, which undergo a metal-insulator transition, creating a gap at the Fermi level, the CDW in VS2 induces a topological metal-metal Lifshitz transition. Our ab initio calculations show anharmonic coupling of transverse and longitudinal phonons to be essential for the formation of the CDW and the full gap above the Fermi level. Additionally, x-ray magnetic circular dichroism reveals the absence of net magnetization in this phase, pointing to a coupled CDW-antiferromagnetic ground state.