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DOE OSTI · 2882370

Discovery of magnetic-field-tunable density modulations and spin tilting in a layered altermagnet

Candelora, Christopher [Boston College, Chestnut Hill, MA (United States)]·Xu, Muxian [Boston College, Chestnut Hill, MA (United States)]·Cheng, Siyu [Boston College, Chestnut Hill, MA (United States)] (ORCID:0009000078259379)·De Vita, Alessandro [Technical Univ. of Berlin (Germany); Fritz Haber Institute of the Max Planck Society, Berlin (Germany)] (ORCID:0000000194132810)·Romanin, Davide [Univ. Paris-Saclay, Palaiseau (France)]·Bigi, Chiara [Synchrotron SOLEIL, Saint-Aubin (France)] (ORCID:0000000309773993)·Petersen, My Bang [Aarhus Univ. (Denmark)]·LaFleur, Alexander [Boston College, Chestnut Hill, MA (United States)]·Castro, Wilber Alfaro [Boston College, Chestnut Hill, MA (United States)] (ORCID:000900078527923X)·Motti, Federico [National Research Council (CNR), Trieste (Italy)]·Orgiani, Pasquale [National Research Council (CNR), Trieste (Italy); AREA Science Park, Trieste (Italy)] (ORCID:0000000210829651)·Vinai, Giovanni [National Research Council (CNR), Trieste (Italy)] (ORCID:000000034882663X)·Calandra, Matteo [Univ. of Trento (Italy)] (ORCID:0000000315052535)·Miwa, Jill [Aarhus Univ. (Denmark)]·Hwang, Younghun [Ulsan College (Korea, Republic of)] (ORCID:0009000876283373)·Wang, Ziqiang [Boston College, Chestnut Hill, MA (United States)] (ORCID:0000000176172886)·Mazzola, Federico [National Research Council (CNR), Napoli (Italy). Inst. for Superconductors, Innovative Materials and Devices (CNR-SPIN); Univ. of Padova (Italy)] (ORCID:0000000253804374)·Zeljkovic, Ilija [Boston College, Chestnut Hill, MA (United States)] (ORCID:0000000199662140)
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Abstract

Altermagnets recently emerged as a new class of magnetic materials, arising from specific spin crystal symmetries. They exhibit a spin-polarized electronic band structure similar to ferromagnets, yet possess zero net magnetization, promising exotic properties. Here we study a layered triangular lattice altermagnet, cobalt-intercalated NbSe 2 using scanning tunneling microscopy and spectroscopy (STM/S). Spectroscopic-imaging STM and spin-polarized STM reveals emergent 2 a 0 tri-directional charge and spin density modulations on the selenium surface. Density functional theory simulations suggest these modulations reflect the underlying cobalt superstructure. We discover that an out-of-plane magnetic field tunes the modulation amplitudes and the electronic density-of-states in a manner dependent on the field direction and strength. This behavior is attributed to the field-induced tilting of cobalt spins, which can have profound implications on the electronic properties of the altermagnet. Our results provide atomic-scale insights to uncover a magnetic-field tunable altermagnetic band structure, highlight the importance of understanding spin canting in altermagnets.

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Candelora, Christopher [Boston College, Chestnut Hill, MA (United States)], Xu, Muxian [Boston College, Chestnut Hill, MA (United States)], Cheng, Siyu [Boston College, Chestnut Hill, MA (United States)] (ORCID:0009000078259379), De Vita, Alessandro [Technical Univ. of Berlin (Germany); Fritz Haber Institute of the Max Planck Society, Berlin (Germany)] (ORCID:0000000194132810), Romanin, Davide [Univ. Paris-Saclay, Palaiseau (France)], Bigi, Chiara [Synchrotron SOLEIL, Saint-Aubin (France)] (ORCID:0000000309773993), Petersen, My Bang [Aarhus Univ. (Denmark)], LaFleur, Alexander [Boston College, Chestnut Hill, MA (United States)], Castro, Wilber Alfaro [Boston College, Chestnut Hill, MA (United States)] (ORCID:000900078527923X), Motti, Federico [National Research Council (CNR), Trieste (Italy)], Orgiani, Pasquale [National Research Council (CNR), Trieste (Italy); AREA Science Park, Trieste (Italy)] (ORCID:0000000210829651), Vinai, Giovanni [National Research Council (CNR), Trieste (Italy)] (ORCID:000000034882663X), Calandra, Matteo [Univ. of Trento (Italy)] (ORCID:0000000315052535), Miwa, Jill [Aarhus Univ. (Denmark)], Hwang, Younghun [Ulsan College (Korea, Republic of)] (ORCID:0009000876283373), Wang, Ziqiang [Boston College, Chestnut Hill, MA (United States)] (ORCID:0000000176172886), Mazzola, Federico [National Research Council (CNR), Napoli (Italy). Inst. for Superconductors, Innovative Materials and Devices (CNR-SPIN); Univ. of Padova (Italy)] (ORCID:0000000253804374), Zeljkovic, Ilija [Boston College, Chestnut Hill, MA (United States)] (ORCID:0000000199662140). 2026-01-31. Discovery of magnetic-field-tunable density modulations and spin tilting in a layered altermagnet. https://doi.org/10.1038/s43246-026-01081-5

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