Highlights
Materials Discovery is a Team Sport for All Ages
As part of its 10-week immersion in hands-on research, PARADIM encourages its REU students to dive in and learn new techniques at the same time they experience the power of team-based research.
Is Hydrogen Essential for Superconductivity in the Nickelates?
Here, PARADIM users from Harvard and Arizona State Universities and their collaborators searched for hydrogen across a wide range of superconducting and non-superconducting layered nickelate films, with different cation and dopant chemistry, structures, growth methods, reduction conditions, and crystalline quality.
Harnessing Machine Learning to Visualize and Understand the Role of Defects in a Metal-to-Insulator Transition in a Charge Density Wave Material
Here, PARADIM’s development of real-time temperature control during cryogenic scanning transmission electron microscopy has enabled its users to image the CDW transition while altering temperature and electric field. Unsupervised machine learning is applied to cluster the five-dimensional, terabyte scale microscopy datasets, and demonstrates a one-to-one correlation between device resistance, CDW phase, and the material microstructure. The team shows that basal dislocations—which are ubiquitous in 2D materials—both nucleate and pin the CDW transition and locally alter the transition temperature (Tc) by nearly ~75 K. Further, the team shows that the dislocation density can be used to engineer device properties.
High-Throughput Aqueous Passivation Behavior of Thin-Film versus Bulk Multi-Principal Element Alloys in Sulfuric Acid
In this work, 177 alloy spots from a CL with varying composition and structure were studied. Bulk samples of (FeCoNi)1-x-yCrxAly were prepared and processed at PARADIM using unique capabilities of its ancillary synthesis facility, including oxygen free arc melting and water jet cutting capabilities to enable quantitative comparisons with the CL spots. Due to varying grain size and the grain boundary dissolution a one-to-one correlation could not be made useful between thin films and bulk.
Simplified (and superior!) Synthesis of Nickelate Superconductors
Here, PARADIM presents X-ray scattering and spectroscopy measurements on a series of NdNiO2+x samples, which reveal that the signatures of charge density wave order are absent in fully reduced, single-phase NdNiO2. The 3a0 superlattice peak instead originates from a partially reduced impurity phase where excess apical oxygens form ordered rows with three-unit-cell periodicity.
Resolving Quantum Oscillations in Insulating YbB12
Here, users from Los Alamos National Lab together with PARADIM propose that the strongly correlated quantum limit can be approached in reverse, starting from an insulating state at zero magnetic field. The identified candidate material, ytterbium boride (YbB12), was grown in single crystal form at PARADIM and studied in high magnetic fields at the NHMFL@LANL. The results not only provide access to a novel quantum phase of matter, but also provide a model that naturally explains how quantum oscillations arise in insulators.
Emergent layer stacking arrangements in c-axis confined MoTe2
The study of 2D transition metal dichalcogenides (TMDs) has largely assumed that the layer stacking in the nanoscale limit adopts one or more of the possible precise stacking sequences found in bulk specimens. This work demonstrates – via atomic resolution imaging – that in fact much greater stacking complexity arises in the thin limit than previously assumed. Given the importance of interlayer stacking on electronic, magnetic, and optical properties, this result suggests greater study of stacking is needed during the characterization of 2D TMDs.
Instabilities of Heavy Magnons in an Anisotropic Magnet
Here, users from Georgia Tech continue their work on single crystals of iron iodide (FeI2) grown by them at the PARADIM Bulk Crystal Facility. In collaboration with Oak Ridge National Lab, they demonstrate that strong quantum interactions exist between three flavors of quasiparticles in the uniaxial spin-one magnet FeI2 through neutron scattering measurements in a transverse magnetic field.
Imaging Nanotextures in Real Space by Inverting X-Ray Diffraction Data
Coherent X-ray diffractive imaging (CXDI) has been widely applied to study the strain distribution in confined systems using an illuminating beam with high spatial coherence. Here, we broaden the capability of CXDI by imaging the strained structural motifs in periodic nanotextured epitaxial thin films with unprecedented nanoscale resolution, exploiting the diffuse scattering pattern from a conventional, partially coherent synchrotron beam. We demonstrate the technique by discovering a previously unreported nanotexture in a Mott insulator epitaxial thin film, which is confirmed by atomic resolution cryo-STEM imaging.
Hump in Hall Measurements Insufficient as Evidence for Skyrmions
Here, the PARADIM In-House Team synthesized a simple bilayer combining a positive anomalous Hall effect (AHE) layer (Sr0.6Ca0.4RuO3) with a negative AHE layer (SrRuO3). The bilayer shows a hump-like feature in the Hall resistivity that closely resembles the one often attributed to skyrmions. Multiple tests for skyrmions were performed, but no evidence of their existence was found.
Nanomolding of metastable Mo4P3
Here, an external (now local) group of researchers came to PARADIM’s Electron Microscopy as well as Theory Facilities to characterize nanomolded molybdenum-phosphide nanowires. Using a poly-crystalline feedstock of MoP, the achieved nanowires are of the composition Mo4P3, a phase metastable at room temperature and ambient pressures, demonstrating a new pathway to the nanofabrication of metastable phases. Density functional theory band structure calculations and resistivity measurements indicate that Mo4P3 is a non-topological metal with resistivity values comparable to other molybdenum phosphide compounds.
A thermally robust transverse thermoelectric
Users from The Ohio State University theoretically predicted axis-dependent conduction polarity in tetragonal α-WSi2—a durable, thermally robust, and oxidation-resistant metal synthesized from earth-abundant elements. Two single crystals of α-WSi2 were prepared at PARADIM’s Bulk Crystal Growth Facility using floating zone techniques, and their anisotropic conduction properties were evaluated. Simultaneous positive and negative thermopowers measured along the [100] and [001] directions, respectively, indicate that this material exhibits axisdependent conduction polarity, which closely matches theoretical predictions.
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