Atomic-scale spin sensing of a 2D $d$-wave altermagnet via helical tunneling

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Main Authors: Wang, Zhuying, Yu, Shuikang, Cheng, Xingkai, Xiao, Xiaoyu, Ma, Wanru, Quan, Feixiong, Song, Hongxi, Zhang, Kunming, Zhang, Yunmei, Ma, Yitian, Liu, Wenhao, Yadav, Priti, Shi, Xiangbiao, Wang, Zhijun, Niu, Qian, Gao, Yang, Xiang, Bin, Liu, Junwei, Wang, Zhenyu, Chen, Xianhui
Format: Preprint
Published: 2025
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author Wang, Zhuying
Yu, Shuikang
Cheng, Xingkai
Xiao, Xiaoyu
Ma, Wanru
Quan, Feixiong
Song, Hongxi
Zhang, Kunming
Zhang, Yunmei
Ma, Yitian
Liu, Wenhao
Yadav, Priti
Shi, Xiangbiao
Wang, Zhijun
Niu, Qian
Gao, Yang
Xiang, Bin
Liu, Junwei
Wang, Zhenyu
Chen, Xianhui
author_facet Wang, Zhuying
Yu, Shuikang
Cheng, Xingkai
Xiao, Xiaoyu
Ma, Wanru
Quan, Feixiong
Song, Hongxi
Zhang, Kunming
Zhang, Yunmei
Ma, Yitian
Liu, Wenhao
Yadav, Priti
Shi, Xiangbiao
Wang, Zhijun
Niu, Qian
Gao, Yang
Xiang, Bin
Liu, Junwei
Wang, Zhenyu
Chen, Xianhui
contents Altermagnetism simultaneously possesses nonrelativistic spin responses and zero net magnetization, thus combining advantages of ferromagnetism and antiferromagnetism. This superiority originates from its unique dual feature, i.e., opposite-magnetic sublattices in real space and alternating spin polarization in momentum space enforced by the same crystal symmetry. Therefore, the determination of an altermagnetic order and its unique spin response inherently necessitates atomic-scale spin-resolved measurements in real and momentum spaces, an experimental milestone yet to be achieved. Here, via utilizing the helical edge (hinge) modes of a higher order topological insulator as the spin sensor, we realize spin-resolved scanning tunneling microscopy which enables us to pin down the dual-space feature of a layered $d$-wave altermagnet, KV$_2$Se$_2$O. In real space, atomic-registered mapping demonstrates the checkerboard antiferromagnetic order together with density-wave lattice modulation, and in momentum space, spin-resolved spectroscopic imaging provides a direct visualization of d-wave spin splitting of the band structure. Critically, using this new topology-guaranteed spin filter we directly reveal the unidirectional, spin-polarized quasiparticle excitations originating from the crystal symmetry-paired X and Y valleys around opposite magnetic sublattices simultaneously --the unique spin response for $d$-wave altermagnetism. Our experiments establish a solid basis for the exploration and utilization of altermagnetism in layered materials and further facilitate access to atomic-scale spin sensing and manipulating of 2D quantum materials.
format Preprint
id arxiv_https___arxiv_org_abs_2512_23290
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Atomic-scale spin sensing of a 2D $d$-wave altermagnet via helical tunneling
Wang, Zhuying
Yu, Shuikang
Cheng, Xingkai
Xiao, Xiaoyu
Ma, Wanru
Quan, Feixiong
Song, Hongxi
Zhang, Kunming
Zhang, Yunmei
Ma, Yitian
Liu, Wenhao
Yadav, Priti
Shi, Xiangbiao
Wang, Zhijun
Niu, Qian
Gao, Yang
Xiang, Bin
Liu, Junwei
Wang, Zhenyu
Chen, Xianhui
Mesoscale and Nanoscale Physics
Materials Science
Strongly Correlated Electrons
Altermagnetism simultaneously possesses nonrelativistic spin responses and zero net magnetization, thus combining advantages of ferromagnetism and antiferromagnetism. This superiority originates from its unique dual feature, i.e., opposite-magnetic sublattices in real space and alternating spin polarization in momentum space enforced by the same crystal symmetry. Therefore, the determination of an altermagnetic order and its unique spin response inherently necessitates atomic-scale spin-resolved measurements in real and momentum spaces, an experimental milestone yet to be achieved. Here, via utilizing the helical edge (hinge) modes of a higher order topological insulator as the spin sensor, we realize spin-resolved scanning tunneling microscopy which enables us to pin down the dual-space feature of a layered $d$-wave altermagnet, KV$_2$Se$_2$O. In real space, atomic-registered mapping demonstrates the checkerboard antiferromagnetic order together with density-wave lattice modulation, and in momentum space, spin-resolved spectroscopic imaging provides a direct visualization of d-wave spin splitting of the band structure. Critically, using this new topology-guaranteed spin filter we directly reveal the unidirectional, spin-polarized quasiparticle excitations originating from the crystal symmetry-paired X and Y valleys around opposite magnetic sublattices simultaneously --the unique spin response for $d$-wave altermagnetism. Our experiments establish a solid basis for the exploration and utilization of altermagnetism in layered materials and further facilitate access to atomic-scale spin sensing and manipulating of 2D quantum materials.
title Atomic-scale spin sensing of a 2D $d$-wave altermagnet via helical tunneling
topic Mesoscale and Nanoscale Physics
Materials Science
Strongly Correlated Electrons
url https://arxiv.org/abs/2512.23290