David A. Muller
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View article: Low barrier ZrO <i>x</i> -based Josephson junctions
Low barrier ZrO <i>x</i> -based Josephson junctions Open
The Josephson junction is a crucial element in superconducting devices, and niobium is a promising candidate for the superconducting material due to its large energy gap relative to aluminum. AlOx has long been regarded as the highest qual…
View article: Patchy nanoparticles by atomic stencilling
Patchy nanoparticles by atomic stencilling Open
View article: Author Correction: Superconductivity and normal-state transport in compressively strained La2PrNi2O7 thin films
Author Correction: Superconductivity and normal-state transport in compressively strained La2PrNi2O7 thin films Open
View article: Using Aberrations to Improve Dose-Efficient Tilt-corrected 4D-STEM Imaging
Using Aberrations to Improve Dose-Efficient Tilt-corrected 4D-STEM Imaging Open
Tilt-corrected imaging methods in four-dimensional scanning transmission electron microscopy (4D-STEM) have recently emerged as a new class of direct ptychography methods that are especially useful at low dose. The operation of tilt correc…
View article: Growth of conductive Si-doped α-Ga2O3 by suboxide molecular-beam epitaxy
Growth of conductive Si-doped α-Ga2O3 by suboxide molecular-beam epitaxy Open
We report a two-step film-growth process using suboxide molecular-beam epitaxy (S-MBE) that produces Si-doped α-Ga2O3 with record transport properties. The method involves growing a relaxed α-(AlxGa1−x)2O3 buffer layer on m-plane sapphire …
View article: Dose-efficient cryo-electron microscopy for thick samples using tilt- corrected scanning transmission electron microscopy
Dose-efficient cryo-electron microscopy for thick samples using tilt- corrected scanning transmission electron microscopy Open
View article: Evidence for carrier compensation by gallium vacancies during annealing of highly Si-doped <i>β</i>-Ga2O3
Evidence for carrier compensation by gallium vacancies during annealing of highly Si-doped <i>β</i>-Ga2O3 Open
Net carrier densities in highly Si-doped β-Ga2O3 decrease during thermal annealing as a function of temperature, time, and PO2 for both in situ and implant-doped films. The mechanism for this loss has been attributed to the formation of ga…
View article: A Distributionally Robust Random Utility Model
A Distributionally Robust Random Utility Model Open
This paper introduces a Distributionally Robust Random Utility Model (DRO-RUM) that accounts for misspecification or uncertainty in the distribution of preference shocks (unobserved heterogeneity). By leveraging distributionally robust opt…
View article: Unconventional Superlattice Ordering in Intercalated Transition Metal Dichalcogenide V<sub>1/3</sub>NbS<sub>2</sub>
Unconventional Superlattice Ordering in Intercalated Transition Metal Dichalcogenide V<sub>1/3</sub>NbS<sub>2</sub> Open
The interplay between symmetry and topology in magnetic materials makes it possible to engineer exotic phases and technologically useful properties. A key requirement for these pursuits is achieving control over local crystallographic and …
View article: Strain-induced lead-free morphotropic phase boundary
Strain-induced lead-free morphotropic phase boundary Open
Enhanced susceptibilities in ferroelectrics often arise near phase boundaries between competing ground states. While chemically-induced phase boundaries have enabled ultrahigh electrical and electromechanical responses in lead-based ferroe…
View article: Improving Multislice Electron Ptychography with a Generative Prior
Improving Multislice Electron Ptychography with a Generative Prior Open
Multislice electron ptychography (MEP) is an inverse imaging technique that computationally reconstructs the highest-resolution images of atomic crystal structures from diffraction patterns. Available algorithms often solve this inverse pr…
View article: PtyRAD: A High-Performance and Flexible Ptychographic Reconstruction Framework with Automatic Differentiation
PtyRAD: A High-Performance and Flexible Ptychographic Reconstruction Framework with Automatic Differentiation Open
Electron ptychography has recently achieved unprecedented resolution, offering valuable insights across diverse material systems, including in three dimensions. However, high-quality ptychographic reconstruction is computationally expensiv…
View article: Strain-induced superconductivity in RuO2(100) thin-films
Strain-induced superconductivity in RuO2(100) thin-films Open
Recently, superconductivity was discovered with a superconducting transition temperature (T c ) of 2 K in strained (110)-oriented RuO2 films grown on TiO2(110) single-crystal substrates. In this work, we predict and realize superconductivi…
View article: Defect-Engineered High-Entropy Spinel Oxide@Onion-Like Carbon Catalysts for High-Areal-Energy Rechargeable Zinc–Air Batteries
Defect-Engineered High-Entropy Spinel Oxide@Onion-Like Carbon Catalysts for High-Areal-Energy Rechargeable Zinc–Air Batteries Open
Rechargeable zinc-air batteries (ReZAB) have emerged as the next-generation batteries with several advantages over the conventional lithium-ion battery. In this work, single nanocrystals of inverse-type high-entropy spinel oxides (HESOx, p…
View article: Achieving 0.05 Ω-mm contact resistance in non-alloyed Ti/Au ohmics to <i>β</i>-Ga2O3 by removing surface carbon
Achieving 0.05 Ω-mm contact resistance in non-alloyed Ti/Au ohmics to <i>β</i>-Ga2O3 by removing surface carbon Open
Preserving a contamination-free metal–semiconductor interface in β-Ga2O3 is critical to achieve consistently low resistance (< 1 Ω-mm) ohmic contacts. Here, we report a scanning transmission electron microscopy study on the variation in…
View article: Superconductivity in the Parent Infinite-Layer Nickelate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>NdNiO</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>
Superconductivity in the Parent Infinite-Layer Nickelate Open
We report evidence for superconductivity with onset temperatures up to 11 K in thin films of the infinite-layer nickelate parent compound NdNiO2. A combination of oxide molecular beam epitaxy and atomic hydrogen reduction yields samples wi…
View article: Superconductivity in Tin Telluride Films Grown by Molecular Beam Epitaxy
Superconductivity in Tin Telluride Films Grown by Molecular Beam Epitaxy Open
The intersection of superconductivity and ferroelectricity hosts a wide range of exotic quantum phenomena. Here, we report on the observation of superconductivity in high-quality tin telluride films grown by molecular beam epitaxy. Uninten…
View article: Electron ptychography reveals a ferroelectricity dominated by anion displacements
Electron ptychography reveals a ferroelectricity dominated by anion displacements Open
Sodium niobate, a lead-free ferroic material, hosts delicately-balanced, competing order parameters, including ferroelectric states that can be stabilized by epitaxial strain. Here, we show that the resulting macroscopic ferroelectricity e…
View article: Operando X-ray absorption spectroscopic investigation of electrocatalysts state in anion exchange membrane fuel cells
Operando X-ray absorption spectroscopic investigation of electrocatalysts state in anion exchange membrane fuel cells Open
Capturing the active state of (electro)catalysts under operating conditions, namely operando, is the ultimate objective of (electro)catalyst characterization, enabling the unraveling of reaction mechanisms and advancing (electro)catalyst d…
View article: Lefschetz thimble-inspired weight regularizations for complex Langevin simulations
Lefschetz thimble-inspired weight regularizations for complex Langevin simulations Open
Complex Langevin (CL) is a computational method to circumvent the numerical sign problem with applications in finite-density quantum chromodynamics and the real-time dynamics of quantum field theories. It has long been known that, dependin…
View article: Bright hybrid excitons in molecularly tunable bilayer crystals
Bright hybrid excitons in molecularly tunable bilayer crystals Open
Bilayer crystals, built by stacking crystalline monolayers, generate interlayer potentials that govern excitonic phenomena but are constrained by fixed covalent lattices and orientations. Replacing one layer with an atomically thin molecul…
View article: Violation of Pauli Limit at KTaO3(110) Interfaces
Violation of Pauli Limit at KTaO3(110) Interfaces Open
The superconducting order parameter at the KTaO3 interfaces and its dependence on interface orientation remains a subject of debate. The superconductivity at these interfaces exhibits strong resilience against in-plane magnetic field and v…
View article: Spectra-orthogonal optical anisotropy in wafer-scale molecular crystal monolayers
Spectra-orthogonal optical anisotropy in wafer-scale molecular crystal monolayers Open
Controlling the spectral and polarization responses of two-dimensional (2D) crystals is vital for developing ultra-thin platforms for compact optoelectronic devices. However, independently tuning optical anisotropy and spectral response re…
View article: Super-Resolution Ptychography with Small Segmented Detectors
Super-Resolution Ptychography with Small Segmented Detectors Open
To overcome the spatial resolution limit set by aperture-limited diffraction in traditional scanning transmission electron microscopy, microscopists have developed ptychography enabled by iterative phase retrieval algorithms and high-dynam…
View article: Quantum oscillations of holes in GaN
Quantum oscillations of holes in GaN Open
GaN has emerged to be a major semiconductor akin to silicon due to its revolutionary impacts in solid state lighting, critically enabled by p-type doping, and high-performance radio-frequency and power electronics. Suffering from inefficie…
View article: Atomically resolved imaging of radiation-sensitive metal-organic frameworks via electron ptychography
Atomically resolved imaging of radiation-sensitive metal-organic frameworks via electron ptychography Open
Electron ptychography, recognized as an ideal technique for low-dose imaging, consistently achieves deep sub-angstrom resolution at electron doses of several thousand electrons per square angstrom (e-/Å2) or higher. D…
View article: Resolving Structural Origins for Superconductivity in Strain-Engineered La$_3$Ni$_2$O$_7$ Thin Films
Resolving Structural Origins for Superconductivity in Strain-Engineered La$_3$Ni$_2$O$_7$ Thin Films Open
The discovery of high-temperature superconductivity in bulk La$_3$Ni$_2$O$_7$ under high hydrostatic pressure and, more recently, biaxial compression in epitaxial thin films has ignited significant interest in understanding the interplay b…
View article: Superconductivity and normal-state transport in compressively strained La$_2$PrNi$_2$O$_7$ thin films
Superconductivity and normal-state transport in compressively strained La$_2$PrNi$_2$O$_7$ thin films Open
The discovery of superconductivity under high pressure in Ruddlesden-Popper phases of bulk nickelates has sparked great interest in stabilizing ambient pressure superconductivity in thin-film form using epitaxial strain. Recently, signs of…
View article: Synthesis of superconducting freestanding infinite-layer nickelate heterostructures on the millimetre scale
Synthesis of superconducting freestanding infinite-layer nickelate heterostructures on the millimetre scale Open
View article: Structural properties and recrystallization effects in ion beam modified B20-type FeGe films
Structural properties and recrystallization effects in ion beam modified B20-type FeGe films Open
Disordered iron germanium (FeGe) has recently garnered interest as a testbed for a variety of magnetic phenomena as well as for use in magnetic memory and logic applications. This is partially owing to its ability to host skyrmions and ant…