The chromium-based kagome metal CsCr3Sb5 has garnered significant interest due to its strong electron correlations, intertwined orders and potential for unconventional superconductivity under high pressure. The evolution of magnetic and superconducting interactions as the more frequently studied CsCr3Sb5 is doped to CsCr3Sb5 remains poorly understood. Here, we demonstrate the emergence of a spatially anisotropic Kondo resonance intertwined with the superconducting gap, enabled by introducing magnetic Cr impurities into the kagome superconductor CsCr3Sb5. The addition of dilute Cr impurities not only weakens long range charge density wave order but also produces local magnetic moments that leads to Kondo resonances. We show that the Kondo resonance forms anisotropic, ripple like spatial patterns around individual Cr atoms, breaking all local mirror symmetries. We further reveal that with the emergence of Kondo screening, the coherence peak and depth of superconducting gap with finite zero-energy conductance are enhanced. This suggests that non superconducting carriers at the Fermi surface in the parent compound participate in the Kondo effect, simultaneously screening Cr magnetic moments and increasing the superfluid density. Our findings offer an opportunity to study the interplay between superconductivity and local magnetism in kagome materials.
Kagome lattices facilitate various quantum phases, yet in bulk materials, their kagome flat-bands often interact with bulk bands, suppressing kagome electronic characteristics for hosting these phases. Here, we use density-functional-theory calculations to predict the geometric and electronic structures, as well as the topological and magnetic properties, of a series of MoTe2-x kagome monolayers formed by mirror-twin-boundary (MTB) loops. We analyze nine MTB-loop configurations of varying sizes and arrangements to assess their impact on various properties. Within the intrinsic bandgap of MoTe2, we identify two sets of kagome bands, originating from in-plane and out-of-plane Te p-orbitals at MTB-loop edges and -vertices, respectively. Three configurations exhibit superior stability, while three others show comparable stability. Among these, four display bandgaps and potentially non-zero Z2 topological invariants, suggesting possible topological phases, while the remaining two are metallic and feature Stoner magnetization. These findings guide the design of kagome-based two-dimensional materials with tunable electronic, topological, and magnetic properties.
Breathing kagome materials Nb3X8 (X = F, Cl, Br, I) have attracted broad interest owing to their Mott insulating behavior and stacking-dependent magnetic ground states. However, the role of interlayer coupling in modulating these properties remains underexplored. Here, using density functional theory with Hubbard U corrections, we systematically investigated how interlayer coupling affects the Mott insulating states and magnetic ground states across 24 bilayer stacking configurations for each compound. We found that all bilayers remain Mott insulators, demonstrating robust Mottness. Driven by the competition between interlayer Pauli repulsion and hopping, most stackings favor interlayer AFM order, including conventional and compensated AFM, while some exhibit AFM-FM degeneracy or stabilize interlayer FM. This robustness of Mott states coexisting with tunable interlayer magnetism provides novel analysis and insights for research on breathing kagome Mott insulators.
Deju Zhang, Zhe Wang, Sihang Che, Wei Ji, and Yanning Zhang*
Abstract:
In the field of low-energy-consumption applications, electrical control of magnetism has attracted considerable research attention. Here, we report that the Janus Cr2S2Se monolayer, where Se atoms substitute the upper S layer in the Cr2S3 monolayer, is structural stable. We find that the Janus Cr2S2Se monolayer favors the ferromagnetic configuration with a high Curie temperature of 279 K, and shows semiconducting characteristics with an indirect band gap of 0.44 eV and a valley splitting of 33 meV. By constructing a van der Waals multiferroic heterostructure combined with α-In2Se3 monolayer, its interlayer magnetism can be switched between two types of magnetic coupling via nonvolatile manipulation of the ferroelectric polarization. Our study reveals the switchable magnetism of the Janus Cr2S2Se monolayer, making it promising candidates for use in next-generation low-dimensional spintronics applications.
Yanyan Geng (耿燕燕)†, Manyu Wang (王曼雨)†, Shumin Meng (孟淑敏), Shuo Mi (米烁), Chang Li (李畅), Huiji Hu (胡会吉), Jianfeng Guo (郭剑锋), Rui Xu (许瑞), Fei Pang (庞斐), Wei Ji (季威), Weichang Zhou (周伟昌)* and Zhihai Cheng (程志海)*
Abstract:
Transition-metal dichalcogenides hosting multiple competing structural and electronic phases are thus ideal platforms for constructing polytype heterostructures with emergent quantum properties. However, controlling phase transitions to form diverse heterostructures inside a single crystal remains challenging. In this study, we realize vertical/lateral polytype heterostructures in a hole-doped Mott insulator via thermal annealing-induced structural transitions. Raman spectroscopy, atomic force microscopy and scanning Kelvin probe force microscopy confirm the coexistence of T-H polytype heterostructures. Atomic-scale scanning tunneling microscopy / spectroscopy measurements reveal the transparent effect in 1H/1T vertical heterostructures, where positive bias v oltage induces in a pronounced superposition of the sqrt13 × sqrt13 CDW of the 1T-layer on the 1H-layer. By systematically comparing the 1T/1H and 1T/1T interfaces, we demonstrate that the metallic 1H-layer induces a Coulomb screening effect on the 1T-layer, suppressing the formation of CDW domain walls and forming more ordered electronic states. These results clarify the interfacial coupling between distinct quantum many-body phases and establish a controllable pathway for constructing two-dimensional polytype heterostructures with tunable electronic properties.
