Termination-Dependent Surface States and Magnetic Fingerprints of Chiral Helimagnet Cr1/3TaS2

Abstract

Chiral helimagnets based on intercalated transition-metal dichalcogenides, characterized by nanoscale spin ordering, provide a powerful route to engineer chiral spin textures (e.g., the topologically protected magnetic solitons) and explore emergent electronic functionalities associated with their surface and interface electronic structures. However, despite growing interest, direct experimental studies of termination-dependent surface electronic structures and their temperature-driven magnetic evolution remain largely unexplored, hindering a microscopic understanding of the electronic states that is crucial for the development of low-dimensional spintronic devices. Here, taking Cr_1/3TaS₂ as a representative example, we systematically investigate the termination-dependent surface electronic states of the chiral helimagnets and uncover their distinct temperature evolution across the magnetic transition (T_C ∼ 142 K) by combining high-resolution angle-resolved photoemission spectroscopy with a microfocused beam and surface-state-resolved first-principles calculations. The TaS₂-terminated surface hosts folded monolayer-like TaS₂ bands under the √3 × √3 superlattice potential and a shallow triangular electron pocket at the superlattice K̅ point arising from Cr–Ta orbital hybridization. In contrast, the Cr-terminated surface exhibits reconstructed hole pockets with pronounced magnetic band splitting. This splitting disappears above T_C and closely follows the temperature evolution of the magnetization, providing a direct spectroscopic fingerprint of the underlying magnetic order. In addition, multiple ultranarrow Cr-d-derived surface flat bands are resolved. These findings demonstrate that Cr_1/3TaS₂ serves as a model system in which surface electronic states are strongly coupled to chiral magnetism, with potential relevance to chiral spintronic and valleytronic micro/nanodevices.