Hidden Moir\'e Topology of Low-Symmetry Weyl Surfaces

Cong Li; Zhilong Yang; Hongxiong Liu; Magnus H. Berntsen; Francesco Scali; Dibya Phuyal; Jianfeng Zhang; Timur K. Kim; Jacek Osiecki; Balasubramanian Thiagarajan; Youguo Shi; Tao Xiang; Quansheng Wu; Oscar Tjernberg

arXiv · 2509.10106

Hidden Moir\'e Topology of Low-Symmetry Weyl Surfaces

Cong Li·Zhilong Yang·Hongxiong Liu·Magnus H. Berntsen·Francesco Scali·Dibya Phuyal·Jianfeng Zhang·Timur K. Kim·Jacek Osiecki·Balasubramanian Thiagarajan·Youguo Shi·Tao Xiang·Quansheng Wu·Oscar Tjernberg

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Abstract

Topological materials are defined by the correspondence between bulk topology and boundary states, yet this correspondence becomes enigmatic on low-symmetry surfaces where bulk and surface periodicities are inherently mismatched. Here we reveal a hidden moir\'e topology emerging on the (103) surface of the Weyl semimetal NdAlSi. Angle-resolved photoemission spectroscopy uncovers closed Fermi-arc loops and momentum-space moir\'e modulations, phenomena unanticipated in conventional topological theory. We show that these emerge from incomplete bulk projection and multi-cell interference governed by a least-common-multiple framework. Least-common-multiple guided DFT and Green's-function calculations quantitatively reproduce the observed spectra, establishing the universality of this commensuration rule. These findings transform a long-standing paradox of bulk-boundary correspondence into a new paradigm of momentum-space moir\'e reconstruction, bridging crystalline and quasicrystalline topologies and opening routes to flat-band engineering on complex surfaces.

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Cong Li, Zhilong Yang, Hongxiong Liu, Magnus H. Berntsen, Francesco Scali, Dibya Phuyal, Jianfeng Zhang, Timur K. Kim, Jacek Osiecki, Balasubramanian Thiagarajan, Youguo Shi, Tao Xiang, Quansheng Wu, Oscar Tjernberg. 2025-09-12. Hidden Moir\'e Topology of Low-Symmetry Weyl Surfaces. https://arxiv.org/abs/2509.10106

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