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MA: Fachverband Magnetismus

MA 4: Electron Theory of Magnetism and Correlations

MA 4.1: Vortrag

Montag, 17. März 2025, 09:30–09:45, H19

Tunable Half-Metallicity and Ferromagnetism in Gated single layer g-C3N4 via Nitrogen Lone Pair Depletion. — •Pietro Nicolò Brangi, Francesca Martini, Pier Luigi Cudazzo, and Matteo Calandra — Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo, Italy

Graphitic carbon nitride (g-C3N4) is a promising catalyst for water splitting and hydrogen production, with nitrogen lone pairs arising from broken carbon-nitrogen bonds in its heptazine structure. These strongly localized and weakly hybridized lone pairs form ultraflat bands potentially leading to correlated states when doped.

Using first-principles calculations, we show that field-effect hole-doping in single-layer g-C3N4 depletes these lone pairs, generating ultraflat bands at the Fermi level and unveiling a rich phase diagram. At low hole concentrations, a half-metallic state emerges with tunable magnetization, increasing linearly with carrier density and reaching up to 1 Bohr magneton /3 f.u.. At an integer filling of one hole per cell, a band-insulating ferromagnetic state is stabilized, followed by an interplay of metallic and half-magnetic phases with further doping, ultimately leading to a second ferromagnetic insulating state.

Our work highlights nitrogen-based lone-pair systems as a novel platform for strongly correlated states, with implications for magnetism even at small electric fields, hinting at unexplored potential in photocatalysis.

Keywords: Graphitic carbon nitride; 2D materials; Half-metal; Field-effect transistor; Density Functional Theory