Publications
Synthesis science of SrRuO3 and CaRuO3 epitaxial films with high residual resistivity ratios
Epitaxial SrRuO3 and CaRuO3 films were grown under an excess flux of elemental ruthenium in an adsorption-controlled regime by molecular-beam epitaxy (MBE), where the excess volatile RuOx (x = 2 or 3) desorbs from the growth front leaving behind a single-phase film. By growing in this regime, we were able to achieve SrRuO3 and CaRuO3 films with residual resistivity ratios (Ï300 K/Ï4 K) of 76 and 75, respectively.
X-ray absorption spectroscopy study of annealing process on Sr1-xLaxCuO2 electron-doped cuprate thin films
The superconducting properties of Sr1-xLaxCuO2 thin films are strongly affected by sample preparation procedures, including the annealing step, which are not always well controlled. We have studied the evolution of Cu L2,3 and O K edge x-ray absorption spectra (XAS) of Sr1-xLaxCuO2 thin films as a function of reducing annealing, both qualitatively and quantitatively.
Facilitated recruitment of mesenchymal stromal cells by bone marrow concentrate and platelet rich plasma
Background Biologics containing growth factors are frequently used to enhance healing after musculoskeletal injuries. One mechanism of action is thought to be though the ability of biologics to induce homing and migration of endogenous mesenchymal stromal cells (MSCs) to a target tissue. However, the ability of biologics to stimulate chemotaxis (directed migration of cells) and chemokinesis (increase rate of cell migration) of MSCs is unknown.
Coherent generation of photonic fractional quantum Hall states in a cavity and the search for anyonic quasiparticles
We present and analyze a protocol in which polaritons in a noncoplanar optical cavity form fractional quantum Hall states. We model the formation of these states and present techniques for subsequently creating anyons and measuring their fractional exchange statistics. In this protocol, we use a rapid adiabatic passage scheme to sequentially add polaritons to the system, such that the system is coherently driven from n- to (n+1)-particle Laughlin states. Quasiholes are created by slowly moving local pinning potentials in from outside the cloud.
Excited States of Methylene, Polyenes, and Ozone from Heat-Bath Configuration Interaction
The electronically excited states of methylene (CH2), ethylene (C2H4), butadiene (C4H6), hexatriene (C6H8), and ozone (O3) have long proven challenging due to their complex mixtures of static and dynamic correlations. The semistochastic heat-bath configuration interaction (SHCI) algorithm, which efficiently and systematically approaches the full configuration interaction (FCI) limit, is used to provide close approximations to the FCI energies in these systems.
Temperature-dependence of stress and elasticity in wet-transferred graphene membranes
We report measurements of the mechanical properties of two suspended graphene membranes in the temperature range of 80 K to 550 K. For this entire range, the resonant frequency and quality factor of each device were monitored continuously during cooling and heating. Below 300 K, we have additionally measured the resonant frequency's tunability via electrostatic force, and modeled this data to determine graphene's tension and elastic modulus; both of these parameters are found to be strongly temperature-dependent in this range.
Electrically tunable single- and few-layer MoS2 nanoelectromechanical systems with broad dynamic range
Atomically thin semiconducting crystals [such as molybdenum disulfide (MoS2)] have outstanding electrical, optical, and mechanical properties, thus making them excellent constitutive materials for innovating new two-dimensional (2D) nanoelectromechanical systems (NEMS). Although prototype structures have recently been demonstrated toward functional devices such as ultralow-power, high-frequency tunable oscillators and ultrasensitive resonant transducers, both electrical tunability and large dynamic range (DR) are critical and desirable.
Influence of Strain on the Surface-Oxygen Interaction and the Oxygen Evolution Reaction of SrIrO3
Understanding how physicochemical properties of materials affect the oxygen evolution reaction (OER) has enormous scientific and technological implications for the OER electrocatalyst design. We present our investigation on the role of strain on the surface-oxygen interaction and the OER on well-defined single-termination SrIrO3 films. Our approach employs a combination of molecular-beam epitaxy, electrochemical characterizations, ambient-pressure X-ray photoelectron spectroscopy, and density functional theory (DFT).
Quantitative light microscopy of dense suspensions: Colloid science at the next decimal place
Since the days of Perrin (1908) [1], microscopy methods have played an important role in the study of colloidal suspensions. Along with the continued development of new imaging techniques, colloid scientists have also implemented a sophisticated range of computational analyses. These analysis techniques are often the unsung heroes that hold the promise of unlocking scientific mysteries at the next decimal place of colloid science.
Strong Enhancement of the Spin Hall Effect by Spin Fluctuations near the Curie Point of FexPt1-x Alloys
Robust spin Hall effects (SHE) have recently been observed in nonmagnetic heavy metal systems with strong spin-orbit interactions. These SHE are either attributed to an intrinsic band-structure effect or to extrinsic spin-dependent scattering from impurities, namely, side jump or skew scattering. Here we report on an extraordinarily strong spin Hall effect, attributable to spin fluctuations, in ferromagnetic FexPt1-x alloys near their Curie point, tunable with x.