Correlation driven near-flat band Stoner excitations in a Kagome magnet.

Among condensed matter systems, Mott insulators exhibit diverse properties that emerge from electronic correlations. In itinerant metals, correlations are usually weak, but can also be enhanced via geometrical confinement of electrons, that manifest as 'flat' dispersionless electronic bands. In the fast developing field of topological materials, which includes Dirac and Weyl semimetals, flat bands are one of the important components that can result in unusual magnetic and transport behaviour.

Relationship between Antisite Defects, Magnetism, and Band Topology in MnSbTe Crystals with ≈ 40 K.

MnSbTe has attracted extensive attention because of its rich and adjustable magnetic properties. Here, using a modified crystal growth method, ferrimagnetic MnSbTe crystals with enhanced Curie temperature () of about 40 K with dominant hole-type carriers and intrinsic anomalous Hall effect is obtained. Time- and angle-resolved photoemission spectroscopy reveals that surface states are absent in both antiferromagnetic and ferrimagnetic MnSbTe, implying that they have topologically trivial electronic structures.

Dramatic Plasmon Response to the Charge-Density-Wave Gap Development in 1T-TiSe_{2}.

1T-TiSe_{2} is one of the most studied charge density wave (CDW) systems, not only because of its peculiar properties related to the CDW transition, but also due to its status as a promising candidate of exciton insulator signaled by the proposed plasmon softening at the CDW wave vector. Using high-resolution electron energy loss spectroscopy, we report a systematic study of the temperature-dependent plasmon behaviors of 1T-TiSe_{2}. We unambiguously resolve the plasmon from phonon modes, revealing the existence of Landau damping to the plasmon at finite momentums, which does not support the plasmon softening picture for exciton condensation.

2D-Materials-Based Wearable Biosensor Systems.

As an evolutionary success in life science, wearable biosensor systems, which can monitor human health information and quantify vital signs in real time, have been actively studied. Research in wearable biosensor systems is mainly focused on the design of sensors with various flexible materials. Among them, 2D materials with excellent mechanical, optical, and electrical properties provide the expected characteristics to address the challenges of developing microminiaturized wearable biosensor systems.

Decoupled ultrafast electronic and structural phase transitions in photoexcited monoclinic VO.

Photoexcitation has emerged as an efficient way to trigger phase transitions in strongly correlated materials. There are great controversies about the atomistic mechanisms of structural phase transitions (SPTs) from monoclinic (-) to rutile (-) VO and its association with electronic insulator-metal transitions (IMTs). Here, we illustrate the underlying atomistic processes and decoupling nature of photoinduced SPT and IMT in nonequilibrium states.

Phase Competition in High-Quality Epitaxial Antiferroelectric PbZrO Thin Films.

Antiferroelectric PbZrO has attracted renewed interest in recent years because of its unique properties and wide range of potential applications. However, the nature of antiferroelectricity and its evolution with the electric field and temperature remain controversial, mostly due to the difficulty of obtaining high-quality single-crystal samples. The lack of consensus regarding the phase transition in PbZrO is not only important on a fundamental side but also greatly hinders further applications.

Atomically engineered cobaltite layers for robust ferromagnetism.

Emergent phenomena at heterointerfaces are directly associated with the bonding geometry of adjacent layers. Effective control of accessible parameters, such as the bond length and bonding angles, offers an elegant method to tailor competing energies of the electronic and magnetic ground states. In this study, we construct unit-thick syntactic layers of cobaltites within a strongly tilted octahedral matrix via atomically precise synthesis.

Emergent Magnetic States and Tunable Exchange Bias at 3d Nitride Heterointerfaces.

Interfacial magnetism stimulates the discovery of giant magnetoresistance (MR) and spin-orbital coupling across the heterointerfaces, facilitating the intimate correlation between spin transport and complex magnetic structures. Over decades, functional heterointerfaces composed of nitrides have seldom been explored due to the difficulty in synthesizing high-quality nitride films with correct compositions. Here, the fabrication of single-crystalline ferromagnetic Fe N thin films with precisely controlled thicknesses is reported.

Destabilization of the Charge Density Wave and the Absence of Superconductivity in ScVSn under High Pressures up to 11 GPa.

VSn ( = Sc, Y, or rare earth) is a new family of kagome metals that have a similar vanadium structural motif as VSb ( = K, Rb, Cs) compounds. Unlike VSb, ScVSn is the only compound among the series of VSn that displays a charge density wave (CDW) order at ambient pressure, yet it shows no superconductivity (SC) at low temperatures. Here, we perform a high-pressure transport study on the ScVSn single crystal to track the evolutions of the CDW transition and to explore possible SC.

Discovery of conjoined charge density waves in the kagome superconductor CsVSb.

The electronic instabilities in CsVSb are believed to originate from the V 3d-electrons on the kagome plane, however the role of Sb 5p-electrons for 3-dimensional orders is largely unexplored. Here, using resonant tender X-ray scattering and high-pressure X-ray scattering, we report a rare realization of conjoined charge density waves (CDWs) in CsVSb, where a 2 × 2 × 1 CDW in the kagome sublattice and a Sb 5p-electron assisted 2 × 2 × 2 CDW coexist. At ambient pressure, we discover a resonant enhancement on Sb L-edge (2s→5p) at the 2 × 2 × 2 CDW wavevectors.

Braiding Lateral Morphotropic Grain Boundaries in Homogenetic Oxides.

Interfaces formed by correlated oxides offer a critical avenue for discovering emergent phenomena and quantum states. However, the fabrication of oxide interfaces with variable crystallographic orientations and strain states integrated along a film plane is extremely challenging by conventional layer-by-layer stacking or self-assembling. Here, the creation of morphotropic grain boundaries (GBs) in laterally interconnected cobaltite homostructures is reported.

Reconstruction of Thiospinel to Active Sites and Spin Channels for Water Oxidation.

Water electrolysis is a promising technique for carbon neutral hydrogen production. A great challenge remains at developing robust and low-cost anode catalysts. Many pre-catalysts are found to undergo surface reconstruction to give high intrinsic activity in the oxygen evolution reaction (OER).

Effect of the Interlayer Ordering on the Fermi Surface of Kagome Superconductor CsV_{3}Sb_{5} Revealed by Quantum Oscillations.

The connection between unconventional superconductivity and charge density waves (CDWs) has intrigued the condensed matter community and found much interest in the recently discovered superconducting Kagome family of AV_{3}Sb_{5} (A=K, Cs, Rb). X-ray diffraction and Raman spectroscopy measurements established that the CDW order in CsV_{3}Sb_{5} comprises of a 2×2×4 structure with stacking of layers in a star-of-David (SD) and inverse-star-of-David (ISD) pattern along the c-axis direction. Such interlayer ordering will induce a vast normalization of the electronic ground state; however, it has not been observed in Fermi surface measurements.

Local spectroscopic evidence for a nodeless magnetic kagome superconductor CeRu.

We report muon spin rotation (SR) experiments on the microscopic properties of superconductivity and magnetism in the kagome superconductor CeRuwithTc≃5 K. From the measurements of the temperature-dependent magnetic penetration depth, the superconducting order parameter exhibits nodeless pairing, which fits best to an anisotropic-wave gap symmetry. We further show that theTc/ratio is comparable to that of unconventional superconductors.

Dual Activation of Molecular Oxygen and Surface Lattice Oxygen in Single Atom Cu /TiO Catalyst for CO Oxidation.

The in-depth mechanism on the simultaneous activation of O and surface lattice O on one active metallic site has not been elucidated yet. Herein, we report a strategy for the construction of abundant oxygen activation sites by rational design of Cu /TiO single atom catalysts (SACs). The charge transfer between isolated Cu and TiO support generates abundant Cu and 2-coordinated O sites in Cu -O-Ti hybridization structure, which facilitates the chemisorption and activation of O molecules.

Manipulating the insulator-metal transition through tip-induced hydrogenation.

Manipulating the insulator-metal transition in strongly correlated materials has attracted a broad range of research activity due to its promising applications in, for example, memories, electrochromic windows and optical modulators. Electric-field-controlled hydrogenation using ionic liquids and solid electrolytes is a useful strategy to obtain the insulator-metal transition with corresponding electron filling, but faces technical challenges for miniaturization due to the complicated device architecture. Here we demonstrate reversible electric-field control of nanoscale hydrogenation into VO with a tunable insulator-metal transition using a scanning probe.

CO Hydrogenation over Copper/ZnO Single-Atom Catalysts: Water-Promoted Transient Synthesis of Methanol.

The hydrogenation of CO by renewable power-generated hydrogen offers a promising approach to a sustainable carbon cycle. However, the role of water during CO hydrogenation is still under debate. Herein, we demonstrated that either too low or too high contents of water hampered the methanol synthesis over Cu/ZnO based catalysts.

Tunable topological Dirac surface states and van Hove singularities in kagome metal GdVSn.

Transition-metal-based kagome materials at van Hove filling are a rich frontier for the investigation of novel topological electronic states and correlated phenomena. To date, in the idealized two-dimensional kagome lattice, topologically Dirac surface states (TDSSs) have not been unambiguously observed, and the manipulation of TDSSs and van Hove singularities (VHSs) remains largely unexplored. Here, we reveal TDSSs originating from a ℤ bulk topology and identify multiple VHSs near the Fermi level () in magnetic kagome material GdVSn.

Enhanced oxygen evolution over dual corner-shared cobalt tetrahedra.

Developing efficient catalysts is of paramount importance to oxygen evolution, a sluggish anodic reaction that provides essential electrons and protons for various electrochemical processes, such as hydrogen generation. Here, we report that the oxygen evolution reaction (OER) can be efficiently catalyzed by cobalt tetrahedra, which are stabilized over the surface of a Swedenborgite-type YBCoO material. We reveal that the surface of YBaCoO possesses strong resilience towards structural amorphization during OER, which originates from its distinctive structural evolution toward electrochemical oxidation.

Perovskite-Socketed Sub-3 nm Copper for Enhanced CO Electroreduction to C.

In situ socketing metal nanoparticles onto perovskite oxides has shown great potential in heterogeneous catalysis, but its employment in boosting ambient CO electroreduction (CER) is unexplored. Here, a CER catalyst of perovskite-socketed sub-3 nm Cu equipped with strong metal-support interactions (SMSIs) is constructed to promote efficient and stable CO -to-C conversion. For such a catalyst, plentiful sub-3 nm ellipsoid Cu particles are homogeneously and epitaxially anchored on the perovskite backbones, with concomitant creation of significant SMSIs.

Spatially Resolved Stimulation for the Controlled Debromination in Single Molecules on a Surface.

A controlled chemical reaction on a specific bond in a single molecule is an inevitable step toward atomic engineering and fabrication. Here, we explored the debromination of a single 9,10-dibromoanthracene (DBA) molecule on a surface as stimulated by the voltage pulse through the tip of a scanning tunneling microscope (STM). A voltage threshold of about 2.

Pressure-Induced Metallization of Lead-Free Halide Double Perovskite (NH ) PtI.

Metallization has recently garnered significant interest due to its ability to greatly facilitate chemical reactions and dramatically change the properties of materials. Materials displaying metallization under low pressure are highly desired for understanding their potential properties. In this work, the effects of the pressure on the structural and electronic properties of lead-free halide double perovskite (NH ) PtI are investigated systematically.

Laser-induced enhancement of vertical polarization in ferroelectric bilayer WTe.

Light-matter interaction is one of the key means to manipulate the structural and electronic properties of materials, especially in two-dimensional (2D) layered materials, which are optically accessible due to their atomic thickness. We propose that an ultrashort laser pulse could drastically enhance the ferroelectric polarization of bilayer WTeby our real-time time-dependent density functional theory simulations. It is noted that bilayer WTeis a 2D sliding ferroelectric material recently discovered whose vertical polarization can be controlled by a slight horizontal displacement.

Step-Climbing Epitaxy of Layered Materials with Giant Out-of-Plane Lattice Mismatch.

Heteroepitaxy with large lattice mismatch remains a great challenge for high-quality epifilm growth. Although great efforts have been devoted to epifilm growth with an in-plane lattice mismatch, the epitaxy of 2D layered crystals on stepped substrates with a giant out-of-plane lattice mismatch is seldom reported. Here, taking the molecular-beam epitaxy of 2D semiconducting Bi O Se on 3D SrTiO substrates as an example, a step-climbing epitaxy growth strategy is proposed, in which the n-th (n = 1, 2, 3…) epilayer climbs the step with height difference from out-of-plane lattice mismatch and continues to grow the n+1-th epilayer.

Pressure-induced monotonic enhancement of T to over 30 K in superconducting PrSrNiO thin films.

The successful synthesis of superconducting infinite-layer nickelate thin films with the highest T ≈ 15 K has ignited great enthusiasm for this material class as potential analogs of the high-T cuprates. Pursuing a higher T is always an imperative task in studying a new superconducting material system. Here we report high-quality PrSrNiO thin films with T ≈ 17 K synthesized by carefully tuning the amount of CaH in the topotactic chemical reduction and the effect of pressure on its superconducting properties by measuring electrical resistivity under various pressures in a cubic anvil cell apparatus.