1D Flat Bands in Phosphorene Nanoribbons with Pentagonal Nature.

Materials with flat bands can serve as a promising platform to investigate strongly interacting phenomena. However, experimental realization of ideal flat bands is mostly limited to artificial lattices or moiré systems. Here, a general way is reported to construct 1D flat bands in phosphorene nanoribbons (PNRs) with a pentagonal nature: penta-hexa-PNRs and penta-dodeca-PNRs, wherein the corresponding 1D flat bands are directly verified by using angle-resolved photoemission spectroscopy.

Van der Waals Electrides.

ConspectusElectrides make up a fascinating group of materials with unique physical and chemical properties. In these materials, excess electrons do not behave like normal electrons in metals or form any chemical bonds with atoms. Instead, they "float" freely in the gaps within the material's structure, acting like negatively charged particles called anions (see the graph).

Highly Efficient Spin Injection and Readout Across Van Der Waals Interface.

Spin injection, transport, and detection across the interface between a ferromagnet and a spin-carrying channel are crucial for energy-efficient spin logic devices. However, interfacial conductance mismatch, spin dephasing, and inefficient spin-to-charge conversion significantly reduce the efficiency of these processes. In this study, it is demonstrated that an all van der Waals heterostructure consisting of a ferromagnet (FeGeTe) and Weyl semimetal enables a large spin readout efficiency.

Decoding Upconversion-Emitting Phase in Complex Composites Through Single-Particle-Level Upconversion Imaging and Density Functional Theory Calculations.

The crystal structure and phase stability of a host lattice plays an important role in efficient upconversion phenomena. In stable hosts, lanthanides doping should not generally change the crystal structure of the host itself. But when phase of a system drastically changes after lanthanide doping resulting in multiple phases, accurate identification of upconverting phase remains a challenge.

Non-centrosymmetric topological phase probed by non-linear Hall effect.

Non-centrosymmetric topological material has attracted intense attention due to its superior characteristics as compared with the centrosymmetric one, although probing the local quantum geometry in non-centrosymmetric topological material remains challenging. The non-linear Hall (NLH) effect provides an ideal tool to investigate the local quantum geometry. Here, we report a non-centrosymmetric topological phase in ZrTe, probed by using the NLH effect.

A versatile model with three-dimensional triangular lattice for unconventional transport and various topological effects.

The finite Berry curvature in topological materials can induce many subtle phenomena, such as the anomalous Hall effect (AHE), spin Hall effect (SHE), anomalous Nernst effect (ANE), non-linear Hall effect (NLHE) and bulk photovoltaic effects. To explore these novel physics as well as their connection and coupling, a precise and effective model should be developed. Here, we propose such a versatile model-a 3D triangular lattice with alternating hopping parameters, which can yield various topological phases, including kagome bands, triply degenerate fermions, double Weyl semimetals and so on.

Interplay of the charge density wave transition with topological and superconducting properties.

Exotic phenomena due to the interplay of different quantum orders have been observed and the study of these phenomena has emerged as a new frontier in condensed matter research, especially in the two-dimensional limit. Here, we report the coexistence of charge density waves (CDWs), superconductivity, and nontrivial topology in monolayer 1H-MSe (M = Nb, Ta) triggered by momentum-dependent electron-phonon coupling through electron doping. At a critical electron doping concentration, new 2 × 2 CDW phases emerge with nontrivial topology, Dirac cones, and van Hove singularities.

Water binding and hygroscopicity in π-conjugated polyelectrolytes.

The presence of water strongly influences structure, dynamics and properties of ion-containing soft matter. Yet, the hydration of such matter is not well understood. Here, we show through a large study of monovalent π-conjugated polyelectrolytes that their reversible hydration, up to several water molecules per ion pair, occurs chiefly at the interface between the ion clusters and the hydrophobic matrix without disrupting ion packing.

Coexistence of ferromagnetism and charge density waves in monolayer LaBr.

Charge density waves (CDWs), a common phenomenon of periodic lattice distortions, often suppress ferromagnetism in two-dimensional (2D) materials, hindering their magnetic applications. Here, we report a novel CDW that generates 2D ferromagnetism instead of suppressing it, through the formation of interstitial anionic electrons as the charge modulation mechanism. first-principles calculations and a low-energy effective model, we find that the highly symmetrical monolayer LaBr undergoes a 2 × 1 CDW transition to a magnetic semiconducting T' phase.

Intertwining of Magnetism and Charge Ordering in Kagome FeGe.

Recent experiments report a charge density wave (CDW) in the antiferromagnet FeGe, but the nature of the charge ordering and the associated structural distortion remains elusive. We discuss the structural and electronic properties of FeGe. Our proposed ground state phase accurately captures atomic topographies acquired by scanning tunneling microscopy.

Realizing Two-Dimensional Supramolecular Arrays of a Spin Molecule via Halogen Bonding.

Well-ordered spin arrays are desirable for next-generation molecule-based magnetic devices, yet their synthetic method remains a challenging task. Herein, we demonstrate the realization of two-dimensional supramolecular spin arrays on surfaces via halogen-bonding molecular self-assembly. A bromine-terminated perchlorotriphenylmethyl radical with net carbon spin was synthesized and deposited on Au(111) to achieve two-dimensional supramolecular spin arrays.

Manipulation of the Topological Ferromagnetic State in a Weyl Semimetal by Spin-Orbit Torque.

Magnetic Weyl semimetals (MWSMs) exhibit unconventional transport phenomena, such as large anomalous Hall (and Nernst) effects, which are absent in spatial inversion asymmetry WSMs. Compared with its nonmagnetic counterpart, the magnetic state of a MWSM provides an alternative way for the modulation of topology. Spin-orbit torque (SOT), as an effective means of electrically controlling the magnetic states of ferromagnets, may be used to manipulate the topological magnetic states of MWSMs.

Efficient Spin-Orbit Torque Switching in a Perpendicularly Magnetized Heusler Alloy MnPtGe Single Layer.

Electrically manipulating magnetic moments by spin-orbit torque (SOT) has great potential applications in magnetic memories and logic devices. Although there have been rich SOT studies on magnetic heterostructures, low interfacial thermal stability and high switching current density still remain an issue. Here, highly textured, polycrystalline Heusler alloy MnPtGe (MPG) films with various thicknesses are directly deposited onto thermally oxidized silicon wafers.

Ultrathin quantum light source with van der Waals NbOCl crystal.

Interlayer electronic coupling in two-dimensional materials enables tunable and emergent properties by stacking engineering. However, it also results in significant evolution of electronic structures and attenuation of excitonic effects in two-dimensional semiconductors as exemplified by quickly degrading excitonic photoluminescence and optical nonlinearities in transition metal dichalcogenides when monolayers are stacked into van der Waals structures. Here we report a van der Waals crystal, niobium oxide dichloride (NbOCl), featuring vanishing interlayer electronic coupling and monolayer-like excitonic behaviour in the bulk form, along with a scalable second-harmonic generation intensity of up to three orders higher than that in monolayer WS.

Probing the Origin of Chiral Charge Density Waves in the Two-Dimensional Limits.

Chirality generates spontaneous symmetry breaking and profoundly influences the topology, charge, and spin orders of materials. The chiral charge density wave (CDW) exhibits macroscopic chirality in the achiral crystal during the spontaneous electronic phase transitions. However, the mechanism of chiral CDW formation is shrouded in controversy.

Unveiling Interstitial Anionic Electron-Driven Ultrahigh K-Ion Storage Capacity in a Novel Two-Dimensional Electride Exemplified by ScSi.

Two-dimensional (2D) electrides, characterized by excess interstitial anionic electron (IAE) in a crystalline 2D material, offer promising opportunities for the development of electrode materials, in particular in rechargeable metal-ion batteries applications. Although a few such potential electride materials have been reported, they generally show low metal-ion storage capacity, and the effect of IAE on the ion storage performance remains elusive so far. Here we report a novel 2D electride, [ScSi]·1e, with fascinating IAE-driven high alkali metal-ion storage capacity.

Real-Space Investigation of the Multiple Halogen Bonds by Ultrahigh-Resolution Scanning Probe Microscopy.

The chemical bond is of central interest in chemistry, and it is of significance to study the nature of intermolecular bonds in real-space. Herein, non-contact atomic force microscopy (nc-AFM) and low-temperature scanning tunneling microscopy (LT-STM) are employed to acquire real-space atomic information of molecular clusters, i.e.

MBE-grown ultrathin PtTe films and their layer-dependent electronic structures.

2D platinum ditelluride (PtTe) has received significant attention for 2D photodetector applications due to its novel physical properties. One of the critical factors that affect device performance is the film quality. Here, using molecular beam epitaxy, we investigate the role of growth temperature in determining the film quality of PtTe on highly oriented pyrolytic graphite, and unveil its layer-dependent electronic properties by X-ray photoelectron spectroscopy, Raman spectroscopy, and scanning tunneling microscopy/spectroscopy (STM/STS), as well as density functional theory (DFT) calculations.

Epitaxial Growth of Ultraflat Bismuthene with Large Topological Band Inversion Enabled by Substrate-Orbital-Filtering Effect.

Quantum spin Hall (QSH) systems hold promises of low-power-consuming spintronic devices, yet their practical applications are extremely impeded by the small energy gaps. Fabricating QSH materials with large gaps, especially under the guidance of design principles, is essential for both scientific research and practical applications. Here, we demonstrate that large on-site atomic spin-orbit coupling can be directly exploited via the intriguing substrate-orbital-filtering effect to generate large-gap QSH systems and experimentally realized on the epitaxially synthesized ultraflat bismuthene on Ag(111).

AgS monolayer: an ultrasoft inorganic Lieb lattice.

Lieb lattice, a two-dimensional edge-centered square lattice, has attracted considerable interest due to its exotic electronic and topological properties. Although various optical and photonic Lieb lattices have been experimentally demonstrated, it remains challenging for an electronic Lieb lattice to be realized in real material systems. Here, based on first-principles calculations and tight-binding modeling, a silver sulfide (AgS) monolayer is reported as a long-sought-after inorganic electronic Lieb lattice.

Room Temperature Ferromagnetism of Monolayer Chromium Telluride with Perpendicular Magnetic Anisotropy.

The realization of long-range magnetic ordering in 2D systems can potentially revolutionize next-generation information technology. Here, the successful fabrication of crystalline Cr Te monolayers with room temperature (RT) ferromagnetism is reported. Using molecular beam epitaxy, the growth of 2D Cr Te films with monolayer thickness is demonstrated at low substrate temperatures (≈100 °C), compatible with Si complementary metal oxide semiconductor technology.