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DS: Fachverband Dünne Schichten

DS 12: 2D Materials I

DS 12.6: Vortrag

Mittwoch, 11. März 2026, 11:00–11:15, REC/C213

Magnetoelectric flat band induced by a √3 × √3 charge density wave in monolayer CrSe₂ — •Victor Pardo¹, Pablo Savino Real¹, Carmen Fuente Santiago¹, Jan Phillips², Javier Corral Sertal¹, Adolfo Otero Fumega³, and Santiago Blanco Canosa⁴ — ¹Instituto de Materiais iMATUS, Universidade de Santiago de Compostela, E-15782 Campus Sur s/n, Santiago de Compostela, Spain — ²Iberian International Nanotechnology Laboratory, INL Braga, Portugal — ³Department of Applied Physics, Aalto University, 02150 Espoo, Finland — ⁴Donostia International Physics Center (DIPC), San Sebastián, Spain

We investigate the electronic and magnetic properties of the √3×√3 charge-density-wave (CDW) phase of CrSe₂ using first-principles calculations within density functional theory. We find that the most stable configuration corresponds to a ferromagnetic ground state, which hosts a remarkably flat electronic band exactly at the Fermi level. We show that the flat band derives from an a_1g-like component of the Cr t_2g manifold in a trigonal environment, combined with bonding–antibonding splittings induced by the formation of Cr trimers in the CDW structure. Strong hybridization between Cr d and Se p orbitals is crucial for stabilizing this band exactly at the Fermi level. Spin–orbit coupling affects only the remaining d bands, leaving the flat band intact. We establish how to tune the existence of this flat-band by relating it to the electric polarization caused by the CDW, hence describing a mechanism to turn on/off strong correlations with an external tuning parameter such as an electric field.

Keywords: two-dimensional materials; transition metal dichalcogenides; flat bands; charge density waves; multiferroics