Localized Spin Textures Stabilized by Geometry-Induced Strain in 2D Magnet FeGeTe.

Strain engineering promises to enable manipulation and control of the properties of exfoliated flakes of 2D van der Waals (vdW) ferromagnets for spintronic applications. However, while previous studies of strain effects have focused on global properties, the impact on local magnetic spin textures remains unexplored. Here, manipulation of magnetism in the 2D ferromagnet FeGeTe (FGT) is demonstrated using geometry-induced strain.

Deformed One-Dimensional Covalent Organic Polymers for Enhanced CO Electroreduction to Methanol.

Spatially arranged molecular catalysts in polymeric frameworks, typically in a layered structure, are emerging strategies to mitigate the molecular aggregation and improve the catalytic performance. However, the effect of local coordination induced by polymerization remains underexplored. Here, we develop one-dimensional cobalt-tetra-amino-phthalocyanine-based covalent organic polymers (1D-COP) for the electrochemical CO reduction reaction (CORR).

Combining Fast Exploration with Accurate Reweighting in the OPES-eABF Hybrid Sampling Method.

On-the-fly probability enhanced sampling (OPES) has recently been introduced [Invernizzi, M.; Parrinello, M. 2022, 18, 3988-3996], with important improvements over the highly popular metadynamics methods.

Atomic-Scale Dynamics at the Interface of Doped Liquid Gallium: Contrasting Effects of Gallium Oxide and Vacuum.

Liquid gallium exhibits a unique, geometrically structured surface that directly influences the diffusion and coalescence of metal solutes at its surface. The complex interplay between different chemical species and gallium's unusual interfacial properties remains poorly understood, yet it plays a crucial role in controlling dopant dynamics, with applications spanning catalysis, nanoscale fabrication, flexible electronics, and liquid metal batteries. Herein, large-scale simulations with -trained machine learning force fields reveal strikingly different interactions of Ag, Au, Bi, Li, Pt, and Sn with liquid gallium interfaces, including both liquid-vacuum and liquid-gallium oxide boundaries.

Trends in the electronic and geometric structures of doped two-dimensional quasi-hexagonal C.

Density functional theory calculations are used to assess the effect of dopant removal within the experimental quasi-hexagonal MgC material [Meirzadeh , , 2023, , 71-76]. A number of geometries at each dopant ratio are considered, with each dopant ratio displaying a wide range of possible electronic structures. As such, the electronic properties are found to depend primarily on geometric factors, rather than on dopant ratios.

Assessing the Impact of Li Concentration and Stacking Faults in the Aliovalent-Substituted Ionic Conductor LiScCl.

Halide electrolytes have gained interest due to their decent conductivities in the mS·cm range and wide electrochemical stability windows. The ionic transport can be influenced by changing the Li concentration in the structure. Due to the high cost of the rare-earth elements in the halide electrolytes, the substitution of lower-cost elements is favored.

Energy-Filtered Excited States and Real-Time Dynamics Served in a Contour Integral.

It is observed that the Cauchy integral formula (CIF) can be used to represent holomorphic functions of diagonalizable operators on a finite domain. This forms the theoretical foundation for applying various operators in the form of a contour integral to a state, while filtering away eigen-components that are not included by the contour. As a special case, the identity operator in the integral form─the Riesz projector─is used to design an algorithm for finding a given number of eigen-pairs whose energies are close to a specified value in the equation-of-motion coupled cluster singles and doubles (EOM-CCSD) framework, with applications to calculate core excited states of molecules which is relevant for the X-ray absorption spectroscopy (XAS).

Unveiling the Effects of Hydroxyl-Induced Trap States on the Charge Transport in p- and n-Channel Organic Field-Effect Transistors through Variable-Temperature Characterization.

Trap states at the gate dielectric-organic semiconductor (OSC) interface are one of the main sources of extrinsic traps in organic field-effect transistors (OFETs). However, they are often overlooked and their effects on the charge transport are attributed to the exposure of devices to ambient air. Here a first variable-temperature transfer length method characterization of both p- and n-channel OFETs under full high vacuum conditions is reported.

Probing amplified Josephson plasmons in YBaCuO by multidimensional spectroscopy.

The nonlinear driving of collective modes in quantum materials can lead to a number of striking non-equilibrium functional responses, which merit a comprehensive exploration of underlying dynamics. However, the coherent coupling between nonlinearly-driven modes frequently involves multiple mode coordinates at once, and is often difficult to capture by one-dimensional pump probe spectroscopy. One example is phonon-mediated amplification of Josephson plasmons in YBaCuO, a phenomenon likely associated with the mysterious superconducting-like optical response observed in this material.

Spin correlations in the nematic quantum disordered state of FeSe.

The quantum-disordered state in FeSe, intertwined with superconductivity and nematicity, has been a research focus in iron-based superconductors. However, the intrinsic spin excitations across the entire Brillouin zone in detwinned FeSe, crucial for understanding its magnetism and superconductivity, have remained unresolved. Using inelastic neutron scattering, we reveal that stripe spin excitations (Q = (1, 0)/(0, 1)) exhibit the C symmetry, while Néel spin excitations (Q = (1, 1)) retain C symmetry within the nematic state.

A Platform for the Development of Highly Red-Shifted Azobenzene-Based Optical Tools.

Azobenzenes are versatile photoswitches that can be used to generate elaborate optical tools, including photopharmaceuticals. However, the targeted application-guided design of new photoswitches with specific properties remains challenging. We have developed synthetic protocols for derivatives of the dfdc (di-ortho-fluoro-di-ortho-chloro) azobenzene scaffold with chemical alterations in the para-/ortho-positions and performed an in-depth study into the effects of their structures on their photophysical properties with an emphasis on the n → π* absorption band using NMR, UV-vis, and X-ray analysis.

Electronic structure and resonant inelastic x-ray scattering in TaNiSe.

We study the electronic structure of TaNiSein its low-temperature semiconducting phase, using resonant inelastic x-ray scattering (RIXS) at the Taedge. We also investigate the electronic properties of TaNiSewithin the density-functional theory (DFT) using the generalized gradient approximation in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. While ARPES, dc transport, and optical measurements indicate that TaNiSeis a small band-gap semiconductor, DFT gives a metallic nonmagnetic solution in TaNiSe.

Quantum Size Effects on Andreev Transport in Nb/Au/Nb Josephson Junctions: A Combined Ab Initio and Experimental Study.

We have measured the critical current density, superconducting coherence length, and superconducting transition temperature of single-domain, epitaxially grown Nb(110)/Au(111)/Nb(110) trilayers, all of which show a nonmonotonic dependence on the thickness of the Au layer. These results are compared with the predictions of a relativistic, ab initio theory, which incorporates superconducting correlations. We find good agreement with experiment, coming from a rich interplay between superconducting proximity and quantum size effects, mediated by Andreev bound states.

Visualizing hot carrier dynamics by nonlinear optical spectroscopy at the atomic length scale.

Probing and manipulating the spatiotemporal dynamics of hot carriers in nanoscale metals is crucial to a plethora of applications ranging from nonlinear nanophotonics to single-molecule photochemistry. The direct investigation of these highly non-equilibrium carriers requires the experimental capability of high energy-resolution (~ meV) broadband femtosecond spectroscopy. When considering the ultimate limits of atomic-scale structures, this capability has remained out of reach until date.

An embedding scheme for constraint-based orbital-optimized excitations in molecular and bulk environments.

We recently presented a novel approach to variationally determine electronically excited states based on constrained density functional theory calculations. The constraint-based orbital-optimized excited state method (COOX) [Kussmann , , 2024, , 8461-8473] allows the evaluation of arbitrary electronic excitations and has several advantages compared to other methods like ΔSCF. In this work, we present an embedding scheme for COOX where the constraint potential is drawn from a sub-system calculation.

Transcorrelated Theory with Pseudopotentials.

The transcorrelated (TC) method performs a similarity transformation on the electronic Schrödinger equation via Jastrow factorization of the wave function. This has demonstrated significant advancements in computational electronic structure theory by improving basis set convergence and compactifying the description of the wave function. In this work, we introduce a new approach that incorporates pseudopotentials (PPs) into the TC framework, significantly accelerating Jastrow factor optimization and reducing computational costs.

Efficient Low-Scaling Calculation of THC-SOS-LR-CC2 and THC-SOS-ADC(2) Excitation Energies Through Density-Based Integral-Direct Tensor Hypercontraction.

In recent years, rapid improvements in computer hardware, as well as theoretical and algorithmic advances have enabled the calculation of ever larger systems in computational chemistry. In this avenue, we present efficient implementations of the scaled opposite-spin (SOS) second-order approximate coupled cluster (CC2) method and the closely related second-order algebraic diagrammatic construction (ADC(2)) method. Our implementations applies the least-squares tensor hypercontraction (THC) approximation, for which a new density-based integral-direct reformulation of the grid-projection of the electron integral tensor is presented.

Insights into Decoupled Solar Energy Conversion and Charge Storage in a 2D Covalent Organic Framework for Solar Battery Function.

Decoupling solar energy conversion and storage in a single material offers a great advantage for off-grid applications. Herein, we disclose a two-dimensional naphthalenediimide (NDI)-based covalent organic framework (COF) exhibiting remarkable solar battery performance when used as a photoanode. Light-induced radicals are stabilized within the framework for several hours, offering on-demand charge extraction for electrical energy production.

Metal Phosphorus Chalcogenide Nanosheet-Modified SnO Electron Transport Layers for Efficient Perovskite Solar Cells.

The electron transport layer (ETL) of tin dioxide (SnO) plays a pivotal role in n-i-p perovskite solar cells (PSCs) by facilitating the extraction of photogenerated electrons and blocking the transport of holes. However, the presence of oxygen vacancies in SnO adversely affects the quality of the ETLs and impairs the electron transport properties, reducing the performance of PSCs. Here, we present a novel interfacial engineering route by incorporating an exfoliated two-dimensional (2D) metal-phosphorus-chalcogen complex of the SnPS nanosheets into the SnO ETL.

Electron deficient oxygen species in highly OER active iridium anodes characterized by X-ray absorption and emission spectroscopy.

Water splitting is a promising technology for storing energy, yet it is challenged by the lack of stable anode materials that can overcome the sluggishness of the oxygen evolution reaction (OER). Iridium oxides are among the most active and stable OER catalysts, however how these materials achieve their performance remains under discussion. The activity of iridium based materials has been attributed to both high metal oxidation states and the appearance of O 2p holes.

Coincident onset of charge order and pseudogap in a homogeneous high-temperature superconductor.

Understanding high-temperature superconductivity in cuprates requires knowledge of the metallic phase it evolves from, particularly the pseudogap profoundly affecting the electronic properties at low carrier densities. A key question is the influence of chemical disorder, which is ubiquitous but exceedingly difficult to model. Using resonant X-ray scattering, we identified two-dimensional charge order in stoichiometric YBaCuO (T = 80 K), which is nearly free of chemical disorder.

Unveiling the Interfacial Reconstruction Mechanism Enabling Stable Growth of the Delafossite PdCoO on AlO and LaAlO.

Delafossites, composed of noble metal () and strongly correlated sublayers (O), form natural superlattices with highly anisotropic properties. These properties hold significant promise for various applications, but their exploitation hinges on the successful growth of high-quality thin films on suitable substrates. Unfortunately, the unique lattice geometry of delafossites presents a significant challenge to thin-film fabrication.

Anomalous Hall Effect due to Magnetic Fluctuations in a Ferromagnetic Weyl Semimetal.

The anomalous Hall effect (AHE) has emerged as a key indicator of time-reversal symmetry breaking (TRSB) and topological features in electronic band structures. Absent of a magnetic field, the AHE requires spontaneous TRSB but has proven hard to probe due to averaging over domains. The anomalous component of the Hall effect is thus frequently derived from extrapolating the magnetic field dependence of the Hall response.

Electronic Structure of the Alternating Monolayer-Trilayer Phase of La_{3}Ni_{2}O_{7}.

Recent studies of La_{3}Ni_{2}O_{7} have identified a bilayer (2222) structure and an unexpected alternating monolayer-trilayer (1313) structure, both of which feature signatures of superconductivity near 80 K under high pressures. Using angle-resolved photoemission spectroscopy, we measure the electronic structure of 1313 samples. In contrast to the previously studied 2222 structure, we find that the 1313 structure hosts a flat band with a markedly different binding energy, as well as an additional electron pocket and band splittings.

Ultrahigh capacitive energy storage through dendritic nanopolar design.

Electrostatic dielectric capacitors with ultrahigh power densities are sought after for advanced electronic and electrical systems owing to their ultrafast charge-discharge capability. However, low energy density resulting from low breakdown strength and suppressed polarization still remains a daunting challenge for practical applications. We propose a microstructural strategy with dendritic nanopolar (DNP) regions self-assembled into an insulator, which simultaneously enhances breakdown strength and high-field polarizability and minimizes energy loss and thus markedly improves energy storage performance and stability.