Fermiology and Skyrmions in Centrosymmetric Magnets: An ARPES perspective

Magnetic skyrmions are topologically nontrivial spin textures that have become a central topic in condensed matter physics owing to their emergent phenomena and potential for spintronic applications. In most non-centrosymmetric materials, they are stabilized by the Dzyaloshinskii–Moriya interaction (DMI), forming skyrmion lattices with sizes of tens to hundreds of nanometers. However, the discovery of skyrmions in centrosymmetric magnets such as Gd₂PdSi₃ [1] and GdRu₂Si₂ [2] has challenged this paradigm. These materials host extremely small skyrmions below 4 nm, the smallest magnetic textures observed in solids. While promising for high-density information technologies, they raise a key question: in the absence of DMI, what stabilizes these spin textures? Proposed mechanisms include geometrical or orbital frustration, dipolar coupling, and itinerant-electron–mediated Ruderman–Kittel–Kasuya–Yosida (RKKY) interactions associated with Fermi surface nesting. Despite extensive efforts, the microscopic origin of skyrmions in centrosymmetric systems remains debated.

Here, we investigate the intrinsic electronic structures of Gd₂PdSi₃ [3] and GdRu₂Si₂ [4] using high-resolution angle-resolved photoemission spectroscopy (ARPES), overcoming challenges related to surface termination and magnetic domains. We identify robust Fermi surface nesting in both compounds, with nesting vectors quantitatively matching magnetic modulation vectors reported by resonant X-ray scattering and neutron studies. In GdRu₂Si₂, we further observe a domain-dependent pseudogap at the nested Fermi surface segments, reconstructing the electronic structure into twofold-symmetric Fermi arcs. The pseudogap (~100 meV) decreases with temperature and vanishes above the Néel temperature, demonstrating its intimate connection to magnetic order. These results provide direct spectroscopic evidence that nesting-driven RKKY interactions stabilize the screw-type spin modulations underlying skyrmion formation in centrosymmetric Gd compounds. Furthermore, magnetic domains in GdRu₂Si₂ can be reconfigured by magnetic fields or thermal cycling, highlighting tunable magnetism and potential for reconfigurable spintronic devices.