Engineering Anomalously Large Electron Transport in Topological Semimetals.

Anomalous transport of topological semimetals has generated significant interest for applications in optoelectronics, nanoscale devices, and interconnects. Understanding the origin of novel transport is crucial to engineering the desired material properties, yet their orders of magnitude higher transport than single-particle mobilities remain unexplained. This work demonstrates the dramatic mobility enhancements result from phonons primarily returning momentum to electrons due to phonon-electron dominating over phonon-phonon scattering.

Much more to explore with an oxidation state of nearly four: Pr valence instability in intermetallic -PrCoGe.

For some intermetallic compounds containing lanthanides, structural transitions can result in intermediate electronic states between trivalency and tetravalency; however, this is rarely observed for praseodymium compounds. The dominant trivalency of praseodymium limits potential discoveries of emergent quantum states in itinerant 4 systems accessible using Pr-based compounds. Here, we use in situ powder x-ray diffraction and in situ electron energy-loss spectroscopy (EELS) to identify an intermetallic example of a dominantly Pr state in the polymorphic system PrCoGe.

Writing and Detecting Topological Charges in Exfoliated FeGeTe.

FeGeTe is a promising two-dimensional (2D) van der Waals (vdW) magnet for practical applications, given its magnetic properties. These include Curie temperatures above room temperature, and topological spin textures─TST (both merons and skyrmions), responsible for a pronounced anomalous Hall effect (AHE) and its topological counterpart (THE), which can be harvested for spintronics. Here, we show that both the AHE and THE can be amplified considerably by just adjusting the thickness of exfoliated FeGeTe, with THE becoming observable even in zero magnetic field due to a field-induced unbalance in topological charges.

Lanthanide Metal-Organic Frameworks Exhibiting Fluoro-Bridged Extended Chains: Synthesis, Crystal Structures, and Magnetic Properties.

Two fluoro-bridged lanthanide-containing metal-organic frameworks (MOFs) were synthesized using 2,2'-bipyridine-4,4'-dicarboxylic acid (BPDC), a fluorinated modulator, and a lanthanide nitrate. The syntheses of MOFs containing Gd or Tb and a closely related MOF structure containing Ho, Gd, or Tb are presented. The presence of the fluorinated metal chains in these MOFs is shown through single crystal X-ray diffraction, energy dispersion X-ray spectroscopy, F nuclear magnetic resonance, and X-ray photoelectron spectroscopy.

Crystal Growth and Physical Properties of Hybrid CoSn-YCoGe Structure Type LnCo(GeSn) (Ln = Y, Gd).

There is an ongoing interest in kagome materials because they offer tunable platforms at the intersection of magnetism and electron correlation. Herein, we examine single crystals of new kagome materials, LnCo(GeSn) (Ln = Y, Gd; = 0.11, 0.

Thickness- and Twist-Angle-Dependent Interlayer Excitons in Metal Monochalcogenide Heterostructures.

Interlayer excitons, or bound electron-hole pairs whose constituent quasiparticles are located in distinct stacked semiconducting layers, are being intensively studied in heterobilayers of two-dimensional semiconductors. They owe their existence to an intrinsic type-II band alignment between both layers that convert these into p-n junctions. Here, we unveil a pronounced interlayer exciton (IX) in heterobilayers of metal monochalcogenides, namely, γ-InSe on ε-GaSe, whose pronounced emission is adjustable just by varying their thicknesses given their number of layers dependent direct band gaps.

Investigating the A B X Homologous Series: A New Platform for Studying Magnetic Praseodymium Based Intermetallics.

The recent discovery of the A B X (A = lanthanide, B = transition metal, X = tetrel) homologous series provides a new platform to study the structure-property relationships of highly correlated electron systems. Several members of Ce Co Ge ( = 1, 4, 5, 6, and ∞) show evidence of heavy electron behavior with complex magnetic interactions. While the Ce analogues have been investigated, only = 1, 2, and ∞ of Pr Co Ge have been synthesized, with = 1 and 2 showing a nonsinglet magnetic ground state.

Supramolecular Reinforcement of a Large-Pore 2D Covalent Organic Framework.

Two-dimensional covalent organic frameworks (2D-COFs) are a class of crystalline porous organic polymers that consist of covalently linked, two-dimensional sheets that can stack together through noncovalent interactions. Here we report the synthesis of a novel COF, called PyCOFamide, which has an experimentally observed pore size that is greater than 6 nm in diameter. This is among the largest pore size reported to date for a 2D-COF.

Strong π-stacking causes unusually large anisotropic thermal expansion and thermochromism.

π-stacking in ground-state dimers/trimers/tetramers of -butoxyphenyl(naphthalene)diimide (BNDI) exceeds 50 kcal ⋅ mol in strength, drastically surpassing that for the [pyrene] excimer (∼30 kcal ⋅ mol; formal bond order = 1) and similar to other weak-to-moderate classical covalent bonds. Cooperative π-stacking in triclinic (BNDI-T) and monoclinic (BNDI-M) polymorphs effects unusually large linear thermal expansion coefficients (α , α , α , β) of (452, -16.8, -154, 273) × 10 ⋅ K and (70.

Fluoro-Bridged Clusters in Rare-Earth Metal-Organic Frameworks.

The modulator 2-fluorobenzoic acid (2-fba) is widely used to prepare RE clusters in metal-organic frameworks (MOFs). In contrast to known RE MOF structures containing hydroxide bridging groups, we report for the first time the possible presence of fluoro bridging groups in RE MOFs. In this report we discuss the synthesis of a holmium-UiO-66 analogue as well as a novel holmium MOF, where evidence of fluorinated clusters is observed.

It Runs in the BaAl Family: Relating the Structure and Properties of Middle Child LnCoGe (Ln = Pr, Nd, and Sm) to its Siblings LnCoGe and LnCoGe.

The BaAl prototype structure and its derivatives have been identified to host several topological quantum materials and noncentrosymmetric superconductors. Single crystals up to ∼3 mm × 3 mm × 5 mm of LnCoGe (Ln = Pr, Nd, and Sm) are obtained via flux growth utilizing Sn as metallic flux. The crystal structure is isostructural to the LuCoSi structure type in the crystallographic space group 2/.

Evidence of a coupled electron-phonon liquid in NbGe.

Whereas electron-phonon scattering relaxes the electron's momentum in metals, a perpetual exchange of momentum between phonons and electrons may conserve total momentum and lead to a coupled electron-phonon liquid. Such a phase of matter could be a platform for observing electron hydrodynamics. Here we present evidence of an electron-phonon liquid in the transition metal ditetrelide, NbGe, from three different experiments.

Antiferromagnetic Order and Spin-Canting Transition in the Corrugated Square Net Compound Cu(TeO)(SO)·HO.

Strongly correlated electrons in layered perovskite structures have been the birthplace of high-temperature superconductivity, spin liquids, and quantum criticality. Specifically, the cuprate materials with layered structures made of corner-sharing square-planar CuO units have been intensely studied due to their Mott insulating ground state, which leads to high-temperature superconductivity upon doping. Identifying new compounds with similar lattice and electronic structures has become a challenge in solid-state chemistry.

Rapidly Reversible Organic Crystalline Switch for Conversion of Heat into Mechanical Energy.

Solid-state thermoelastic behavior-a sudden exertion of an expansive or contractive physical force following a temperature change and phase transition in a solid-state compound-is rare in organic crystals, few are reversible systems, and most of these are limited to a dozen or so cycles before the crystal degrades or they reverse slowly over the course of many minutes or even hours. Comparable to thermosalience, wherein crystal phase changes induce energetic jumping, thermomorphism produces physical work via consistent and near-instantaneous predictable directional force. In this work, we show a fully reversible thermomorphic actuator that is stable at room temperature for multiple years and is capable of actuation for more than 200 cycles at near-ambient temperature.

Fantastic n = 4: CeCoGeSn of the AMX homologous series.

Ce-based intermetallics are of interest due to the potential to study the interplay of localized magnetic moments and conduction electrons. Our work on Ce-based germanides led to the identification of a new homologous series AMX (A = rare earth, M = transition metal, X = tetrels, and n = 1-6). This work presents the single-crystal growth, structure determination, and anisotropic magnetic properties of the n = 4 member of the CeCoGe homologous series.

Ligand Steric Effects of α-Diimine Nickel(II) and Palladium(II) Complexes in the Suzuki-Miyaura Cross-Coupling Reaction.

Nickel catalysts represent a low cost and environmentally friendly alternative to palladium-based catalytic systems for Suzuki-Miyaura cross-coupling (SMC) reactions. However, nickel catalysts have suffered from poor air, moisture, and thermal stabilities, especially at high catalyst loading, requiring controlled reaction conditions. In this report, we examine a family of mono- and dinuclear Ni(II) and Pd(II) complexes with a diverse and versatile α-diimine ligand environment for SMC reactions.

Accessing new magnetic regimes by tuning the ligand spin-orbit coupling in van der Waals magnets.

Van der Waals (VdW) materials have opened new directions in the study of low dimensional magnetism. A largely unexplored arena is the intrinsic tuning of VdW magnets toward new ground states. Chromium trihalides provided the first such example with a change of interlayer magnetic coupling emerging upon exfoliation.

Peroxide-Templated Assembly of a Trimetal Neodymium Complex Single-Molecule Magnet.

In this work, we present a trimetal neodymium complex with two notable qualities. First, the assembly of the complex is templated by peroxide derived from atmospheric oxygen. Second, the bulk material behaves as a superparamagnet, implying that the individual complexes are molecular magnets.

2D-Covalent Organic Frameworks with Interlayer Hydrogen Bonding Oriented through Designed Nonplanarity.

We report the synthesis and characterization of a new class of 2D-covalent organic frameworks, called COFamides, whose layers are held together by amide hydrogen bonds. To accomplish this, we have designed monomers with a nonplanar structure that arises from steric crowding, forcing the amide side groups out of plane with the COF sheets orienting the hydrogen bonds between the layers. The presence of these hydrogen bonds provides significant structural stabilization as demonstrated by comparison to control structures that lack hydrogen bonding capability, resulting in lower surface area and crystallinity.

Crystal Structure and Electronic Properties of New Compound ZrPtSe.

A new ternary nonstoichiometric ZrPtSe has been discovered as a part of effort to dope Zr into the layered transitional metal chalcogenide PtSe. With a new structure type (68), it is the first Pt-based ternary chalcogenide with group 4 elements (Ti, Zr, and Hf). The crystal structure adopts the orthorhombic space group with lattice parameters of = 15.

Characterization of a Holmium 4,4'-Biphenyldicarboxylate Metal-Organic Framework and Its Potential as a Holmium Carrier System.

There is growing interest in Holmium carriers for radiotherapeutic applications. In this work, a holmium-based metal-organic framework (MOF) using the 4,4'-biphenyldicarboxylic acid (H₂BPDC) linker was synthesized and characterized to explore its potential as a radiotherapeutic carrier. The 3D MOF [Ho(BPDC)₂]·(CH₃)₂NH₂ was characterized by single crystal X-ray diffraction, FTIR, TGA and PXRD.

Law and Disorder: Special Stacking Units-Building the Intergrowth CeCoGe.

A new structure type of composition CeCoGe was grown out of a molten Sn flux. CeCoGe crystallizes in the orthorhombic space group Cmcm, with highly anisotropic lattice parameters of a = 4.3293(5) Å, b = 55.

The Role of Crystal Growth Conditions on the Magnetic Properties of LnFeCo Sb (Ln = La and Ce).

Single crystals of LnFeCo SbBi (Ln = La, Ce; 0 ≤ x < 0.5; 0 ≤ y ≤ 0.2) were grown using Bi flux and self-flux methods.

Transition from a 1D Coordination Polymer to a Mixed-Linker Layered MOF.

A novel copper(II) metal-organic framework (MOF) has been synthesized by modifying the reaction conditions of a 1D coordination polymer. The 1D polymer is built by the coordination between copper and 2,2'-(1 H-imidazole-4,5-diyl)di-1,4,5,6-tetrahydropyrimidine (H-L1). The geometry of H-L1 precludes its ability to form extended 3D framework structures.