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Rare-earth magnetic adatoms offer a promising pathway to manipulate the electronic and magnetic properties of topological insulators by locally breaking time-reversal symmetry [1]. In this work, we investigate the interaction of submonolayer erbium (Er) on the surface of Bi₂Te₃ through a comprehensive experimental approach combining synchrotron-based spectroscopy with local probe microscopy [2].
The electronic structure evolution was characterized by X-ray photoemission spectroscopy (XPS) and angle-resolved photoemission spectroscopy (ARPES) at the LOREA beamline of the ALBA Synchrotron, revealing the modification of the topological surface state, including a pronounced reconstruction of the Fermi surface, the opening of a gap at the Dirac point, and momentum-dependent spectral changes induced by Er adsorption. The magnetic properties of the Er adatoms were determined by X-ray magnetic circular dichroism (XMCD) measurements performed at the BOREAS beamline, demonstrating a strong out-of-plane magnetic anisotropy that provides the magnetic symmetry breaking required to modify the topological electronic states. Complementary scanning tunneling microscopy and spectroscopy (STM/STS), carried out at IMDEA Nanociencia, together with quasiparticle interference analysis, provide atomic-scale insight into the adsorption geometry, the local electronic structure, and the resulting changes in the surface scattering processes.
This work provides microscopic insight into the interplay between magnetism and topology at the surface of Bi₂Te₃, establishing rare-earth surface doping as an effective strategy to tailor topological electronic states with atomic-scale precision. These findings open new avenues for engineering magnetic topological phases and represent a significant step toward the realization of phenomena such as the quantum anomalous Hall effect.
[1] B. Muñiz Cano, …, and M. A. Valbuena, “Experimental Demonstration of a Magnetically Induced Warping Transition in a Topological Insulator Mediated by Rare-Earth Surface Dopants ”Nano Lett. 2023, 23, 13, 6249–6258
[2] B. Muñiz Cano, …, M. Garnica and M. A. Valbuena, “Microscopic Insights into Magnetic Warping and Time-Reversal Symmetry Breaking in Topological Surface States of Rare-Earth-Doped Bi2Te3.” Adv. Mater. (2025): e10877. https://doi.org/10.1002/adma.202510877