The charge states of metal adatoms on surfaces play a crucial role in controlling adsorption and interaction behaviors that underpin surface chemistry and catalysis, yet the atomically synthesis of negatively charged metal atoms remains a significant challenge. Here, we report negatively-charged Ag dimer (Ag_2^(δ-)) arrays assembled on Ag(100) surface through coordination with a polycyclic aromatic hydrocarbon, 8,9-diaza-8a-borabenzo[fg]tetracene (DBT), featuring a doping moiety with N-B-N bonds at zigzag edge. The Ag dimers are stabilized by two DBT monomers through N-Ag-N coordination bonding. In contrast to surface Ag atoms, the coordinated dimers display anionic character, as demonstrated by non-contact atomic force microscopy, Kelvin probe force microscopy, x-ray photoelectron spectroscopy, and density functional theory calculations. Neutral dimers Ag_2^0 can be converted from the coordinated complex by tip-induced detachment of one DBT monomer, and showed markedly higher affinity for CO adsorption, a process that is suppressed on (Ag_2^(δ-)). These findings establish an atomically defined platform for stabilizing and controlling anionic metal centers on metallic surfaces, providing a model system for exploring charge-state effects in surface chemistry.
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.
Information units are progressively approaching the fundamental physical limits of the integration density, including in terms of extremely small sizes, multistates and probabilistic traversal. However, simultaneously encompassing all of these characteristics in a unit remains elusive. Here, via real-time in situ electrical monitoring, we clearly observed stochastic alterations of multiple conductance states in Sc2C2@C88. The true random bit sequence generated exhibited an autocorrelation function whose confidence interval fell within ±0.02, demonstrating high-quality randomness. The alterations of multiple conductance states are controllable, that is, whose probability distributions could traverse from “0” to “1”, enabling us to factorize 551 into its prime factors. Furthermore, we proposed a matrix-chain multiplication scheme and experimentally verified the multiplication of two 4 × 4 state-transition matrices with a small maximum error < 0.05. Combined with theoretical calculations, the stochastic but controllable multistates are probably attributed to the rich energy landscape, which could be stepwise changed by the electric field. Our findings reveal extremely small multi-level probabilistic bit for matrix multiplication, which pave the way for ultracompact intelligent electronic devices.
As a fundamental phenomenon in nature, chirality has been extensively studied in molecular structures; however, it remains underexplored at the electronic level. Understanding how structural chirality transfers into electronic states is crucial for uncovering the essence of many chiral effects. In this study, we report the engineering and direct visualization of chiral electronic states within an otherwise planar, achiral hexa-peri-hexabenzocoronene (HBC) framework. By employing atomically precise asymmetric nitrogen doping of HBC through on-surface synthesis, we fabricate a C3-symmetric triaza-HBC on Au(111). Utilizing high-resolution scanning tunneling microscopy and non-contact atomic force microscopy, we resolve the chiral molecular structure of triaza-HBC confined to the surface, as well as the chiral texture of the resulting interfacial electronic states and its evolution at different energies. Density functional theory calculations reveal that these electronic chiral features arise from the molecule's intrinsic chiral orbitals, which hybridize strongly with the metal substrate while still retaining their chiral character. This study not only demonstrates a clear transfer of chirality from molecular structure to the electronic landscape but also provides a versatile platform for the rational design of chiral electronic molecules and 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.
