# Direct observation of a spin-polarized surface Dirac gap in the antiferromagnetic topological insulator NdBi https://mdr.nims.go.jp/datasets/bb44a2d8-d20a-4c0f-9f0b-18597f7d951d ## File - [NCommun_17(2026)10841_Fukushima.pdf](https://mdr.nims.go.jp/filesets/ffa6b25f-56de-407b-a146-1ad81c3caab1/download) ([Detail](https://mdr.nims.go.jp/filesets/ffa6b25f-56de-407b-a146-1ad81c3caab1.md)) ## Id bb44a2d8-d20a-4c0f-9f0b-18597f7d951d ## Local identifier ## Visibility open_to_public ## State published ## Created at 2026-10-16T04:34:04.655229Z ## Updated at 2026-10-18T23:49:18.339669Z ## Published at 2026-10-19T01:30:08.371813Z ## Doi ## First published url https://doi.org/10.1038/s41467-026-77571-4 ## Date published 2026-09-15 ## Recorded date published ## Resource type journal_article ## Manuscript type vor ## Collection ## Title - title: Direct observation of a spin-polarized surface Dirac gap in the antiferromagnetic topological insulator NdBi title_type: original lang: en ## Description - description: "A gapped Dirac cone in antiferromagnetic topological insulators (AFM-TIs) is essential for realizing exotic quantum phenomena, such as the quantum anomalous Hall effect and axion electrodynamics. In the prototypical AFM-TI MnBi2Te4, however, the observed energy gap in the Dirac cone is significantly smaller\r\nthan theoretical predictions or nearly absent. This long-standing discrepancy not only limits the feasibility of high-temperature applications but also hinders a full understanding of the interplay between bulk magnetism and topological surface state, a central issue in topological physics. Here we demonstrate that NdBi, a recently identified AFM-TI, hosts a surface Dirac cone with a sizable gap of 15 meV, in excellent agreement with density functional theory predictions (12 meV). This provides the first unambiguous spectroscopic evidence of an intrinsic magnetic topological insulator in NdBi. This was made possible by high-resolution, laser-based spin- and angle-resolved photoemission spectroscopy, which clearly separates the spin-polarized surface Dirac cone from adjacent bulk states for the first time. We further show that the gap originates from cooperative exchange interactions mediated by both bulk and surface magnetism, driven by strong coupling between localized Nd 4f moments and itinerant carriers. These findings identify NdBi as a rare AFM-TI in which the surface Dirac gap reflects intrinsic magnetism rather than surface-related artifacts. The temperature-tunable nature of this Dirac gap governed by magnetism opens avenues for the realization of high-temperature topological spintronic functionalities." description_type: abstract lang: und ## Creator - name: Yuto Fukushima role: author orcid: https://orcid.org/0009-0004-5820-7001 - name: Hiroyuki S. Suzuki role: author orcid: https://orcid.org/0000-0001-8468-2632 - name: Masayuki Ochi role: author - name: Takuma Nishida role: author - name: Toshiya Ikenobe role: author - name: Hiraku Saito role: author orcid: https://orcid.org/0009-0004-6657-0863 - name: Yuto Kinoshita role: author orcid: https://orcid.org/0000-0002-0785-0011 - name: Kaishu Kawaguchi role: author orcid: https://orcid.org/0000-0002-2211-9841 - name: Hiroaki Tanaka role: author orcid: https://orcid.org/0000-0002-5178-7777 - name: Ayumi Harasawa role: author - name: Takushi Iimori role: author - name: Koichiro Yaji role: author orcid: https://orcid.org/0000-0002-0721-1316 - name: Masashi Tokunaga role: author orcid: https://orcid.org/0000-0002-1401-9381 - name: Taro Nakajima role: author orcid: https://orcid.org/0000-0001-6557-5508 - name: Kiyohisa Tanaka role: author orcid: https://orcid.org/0000-0003-2779-5870 - name: Takahiro Morimoto role: author orcid: https://orcid.org/0000-0003-4825-7377 - name: Ryo Mori role: author orcid: https://orcid.org/0000-0002-8684-9421 - name: Takeshi Kondo role: author orcid: https://orcid.org/0000-0002-3912-5172 ## Contact agent ## Publisher organization: Springer Science and Business Media LLC ## Managing organization ## Keyword - subject: Antiferromagnetic topological insulators schema: not_defined - subject: Angle-resolved photoemission spectroscopy schema: not_defined ## Rights - identifier: https://creativecommons.org/licenses/by/4.0/ ## Other identifier(s) ## Data origin - data_origin_type: other ## Embargo ## Journal - title: Nature Communications issn: '20411723' volume: '17' issue: '1' ## Conference ## Related item ## Funding ## Instrument ## Instrument operator ## Instrument managing organization ## Measurement method ## Specimen ## Chemical composition ## Structure for specimen ## Structural feature for specimen ## Specific property for specimen ## Process for specimen treatment ## Computational method ## Energy level/transition state ## Software ## Custom property ## Fileset - id: ffa6b25f-56de-407b-a146-1ad81c3caab1 filename: NCommun_17(2026)10841_Fukushima.pdf content_type: application/pdf size: 1822851 md5: 3be3ad3dac983b669aa8c3680d6506d2 ## Thumbnail fileset_id: ffa6b25f-56de-407b-a146-1ad81c3caab1 filename: NCommun_17(2026)10841_Fukushima.pdf