Dresden 2026 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 24: 2D Materials IV – Emerging materials and properties
HL 24.10: Talk
Wednesday, March 11, 2026, 12:00–12:15, POT/0081
Robust Orbital-Selective Flat Bands in Transition-Metal Oxychlorides — Xiangyu Luo1, •Ludovica Zullo2, Sahaj Patel1, Dongjin Oh1, Qian Song1, Asish K. Kundu3, Anil Rajapitamahuni3, Elio Vescovo3, Natalia Olszowska4, Rafal Kurleto4, Dawid Wutke4, Giorgio Sangiovanni2, and Riccardo Comin1 — 1Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA — 2Universität Würzburg, 97074 Würzburg, Germany, ct.qmat — 3National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, USA — 4Solaris National Synchrotron Radiation Centre, Jagiellonian University, Czerwone Maki 98, 30-392 Krakow, Poland
Flat electronic bands, which amplify electron correlations by quenching kinetic energy, provide an ideal foundation for exotic quantum phases. Here, we unveil an intrinsic orbital-selective flat-band mechanism in the van der Waals materials NbOCl2 and TaOCl2, directly observed by angle-resolved photoemission spectroscopy (ARPES) and understood through density functional theory (DFT) and Wannier analysis. Crucially, we experimentally demonstrate that this momentum-independent flat band exhibits remarkable robustness, surviving from the bulk crystal down to the few-layer limit at room temperature. Our theoretical analysis traces its origin to the hybridization between Nb-dz2 orbital chains and the Lieb-like dx2-y2 sublattice, which is further reinforced by Peierls dimerization. Our findings uncover a new orbital-selective design principle for realizing flat bands in quantum materials.
Keywords: Flat bands; Charge density waves; Multi-orbital physics