Browsing by Author "Yue, Ziqin"
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Item Kramers nodal lines and Weyl fermions in SmAlSi(Springer Nature, 2023) Zhang, Yichen; Gao, Yuxiang; Gao, Xue-Jian; Lei, Shiming; Ni, Zhuoliang; Oh, Ji Seop; Huang, Jianwei; Yue, Ziqin; Zonno, Marta; Gorovikov, Sergey; Hashimoto, Makoto; Lu, Donghui; Denlinger, Jonathan D.; Birgeneau, Robert J.; Kono, Junichiro; Wu, Liang; Law, Kam Tuen; Morosan, Emilia; Yi, MingKramers nodal lines (KNLs) have recently been proposed theoretically as a special type of Weyl line degeneracy connecting time-reversal invariant momenta. KNLs are robust to spin orbit coupling and are inherent to all non-centrosymmetric achiral crystal structures, leading to unusual spin, magneto-electric, and optical properties. However, their existence in in real quantum materials has not been experimentally established. Here we gather the experimental evidence pointing at the presence of KNLs in SmAlSi, a non-centrosymmetric metal that develops incommensurate spin density wave order at low temperature. Using angle-resolved photoemission spectroscopy, density functional theory calculations, and magneto-transport methods, we provide evidence suggesting the presence of KNLs, together with observing Weyl fermions under the broken inversion symmetry in the paramagnetic phase of SmAlSi. We discuss the nesting possibilities regarding the emergent magnetic orders in SmAlSi. Our results provide a solid basis of experimental observations for exploring correlated topology in SmAlSiItem Embargo Surface Modification of Quantum Materials(2023-09-15) Yue, Ziqin; Yi, Ming; Kono, JunichiroThe tuning of surface electronic structure in quantum materials has emerged as an important research direction with broad implications for both fundamental physics as well as applications. Here we carried out angle-resolved photoemission spectroscopy to characterize the continuous evolution of the electronic band structures in a prototypical three-dimensional topological insulator, Bi2Se3, and a van der Waals ferromagnetic semiconductor, Cr2Ge2Te6, using different approaches of in-situ surface modification. In Bi2Se3, by active hydrogen etching, we demonstrate the gradual removal of Se atoms and the formation of Bi bilayers that directly result in the spatial tuning of the topological surface states. In Cr2Ge2Te6, by surface alkali metal dosing, we observe the appearance and tuning of a Van Hove singularity in the electronic structure and subsequent renormalization of the conduction band, suggesting the tuning of surface charge carriers as a way to modify electronic correlations in 2D materials.