A5059962903- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Magnetic properties of thin films
- Electronic and Structural Properties of Oxides
- High-pressure geophysics and materials
- Rare-earth and actinide compounds
- X-ray Diffraction in Crystallography
- X-ray Spectroscopy and Fluorescence Analysis
- 2D Materials and Applications
- Graphene research and applications
- Theoretical and Computational Physics
- Organic and Molecular Conductors Research
- Multiferroics and related materials
- Advanced X-ray Imaging Techniques
- Boron and Carbon Nanomaterials Research
- Diamond and Carbon-based Materials Research
- Crystallography and Radiation Phenomena
- Perovskite Materials and Applications
- Surface and Thin Film Phenomena
- Inorganic Chemistry and Materials
- Quantum and electron transport phenomena
- Particle Detector Development and Performance
- Electron and X-Ray Spectroscopy Techniques
- Solid-state spectroscopy and crystallography
Brookhaven National Laboratory
2016-2025
Stanford Synchrotron Radiation Lightsource
2025
National Synchrotron Light Source II
2016-2025
Paul Scherrer Institute
2013-2018
Swiss Light Source
2014-2016
Leibniz Institute for Solid State and Materials Research
2010-2016
Canadian Light Source (Canada)
2014
University of British Columbia
2014
European Synchrotron Radiation Facility
2007-2012
European Science Foundation
2012
Conventional two-dimensional electron gases are realized by engineering the interfaces between semiconducting compounds. In 2004, Ohtomo and Hwang discovered that an gas can be also at interface large gap insulators made of transition metal oxides [1]. This finding has generated considerable efforts to clarify underlying microscopic mechanism. Of particular interest is LaAlO3/SrTiO3 system, because it features especially striking properties. High carrier mobility [1], electric field tuneable...
Linear dichroism (LD) in x-ray absorption, diffraction, transport, and magnetization measurements on thin La(0.7)Sr(0.3)MnO(3) films grown different substrates, allow identification of a peculiar interface effect, related just to the presence interface. We report LD signature preferential 3d-e(g)(3z(2)-r(2)) occupation at interface, suppressing double exchange mechanism. This surface orbital reconstruction is opposite that favored by residual strain independent dipolar fields, chemical...
Abstract The metal–insulator transition and the intriguing physical properties of rare-earth perovskite nickelates have attracted considerable attention in recent years. Nonetheless, a complete understanding these materials remains elusive. Here we combine X-ray absorption resonant inelastic scattering (RIXS) spectroscopies to resolve important aspects complex electronic structure nickelates, taking NdNiO 3 thin film as representative example. unusual coexistence bound continuum excitations...
We probe the collective magnetic modes of La2CuO4 and underdoped La2-xSrxCuO4 (LSCO) by momentum resolved resonant inelastic x-ray scattering (RIXS) at Cu L3 edge. For undoped antiferromagnetic sample, we show that single magnon dispersion measured with RIXS coincides one determined neutron scattering, thus demonstrating x rays are an alternative to neutrons in this field. In spin dynamics LSCO, find a branch dispersing up approximately 400 meV coexisting lower energy. The high-energy has...
By resonant inelastic x-ray scattering in the soft regime we probe dynamical multiple-spin correlations antiferromagnetic cuprates La2CuO4 and CaCuO2. High resolution measurements at copper L3 edge allow clear observation of dispersing bimagnon excitations. Theory based on ultrashort core-hole lifetime expansion fits data these coherent spin excitations without free parameters.
We measured high resolution Cu $L_3$ edge resonant inelastic x-ray scattering (RIXS) of the undoped cuprates La$_2$CuO$_4$, Sr$_2$CuO$_2$Cl$_2$, CaCuO$_2$ and NdBa$_2$Cu$_3$O$_6$. The dominant spectral features were assigned to $dd$ excitations we extensively studied their polarization geometry dependence. In a pure ionic picture, calculated theoretical cross sections for those used them fit experimental data with excellent agreement. By doing so, able determine energy symmetry Cu-3$d$...
Abstract Despite mounting evidence that materials imperfections are a major obstacle to practical applications of superconducting qubits, connections between microscopic material properties and qubit coherence poorly understood. Here, we combine measurements transmon relaxation times ( T 1 ) with spectroscopy microscopy the polycrystalline niobium films used in fabrication. By comparing deposited using three different techniques, reveal correlations intrinsic film such as grain size,...
The discovery of superconductivity in a $d^{9-{\delta}}$ nickelate has inspired disparate theoretical perspectives regarding the essential physics this class materials. A key issue is magnitude magnetic superexchange, which relates to whether cuprate-like high-temperature could be realized. We address question using Ni L-edge and O K-edge spectroscopy reduced trilayer $d^{9-1/3}$ La4Ni3O8 associated modeling. magnon energy scale ~80 meV resulting from nearest-neighbor exchange $J = 69(4)4$...
Magnetic van der Waals (vdW) materials have opened new frontiers for realizing novel many-body phenomena. Recently NiPS3 has received intense interest since it hosts an excitonic quasiparticle whose properties appear to be intimately linked the magnetic state of lattice. Despite extensive studies, electronic character, mobility, and interactions exciton remain unresolved. Here we address these issues by measuring with ultra-high energy resolution resonant inelastic x-ray scattering (RIXS)....
Strongly correlated materials respond sensitively to external perturbations such as strain, pressure, and doping. In the recently discovered superconducting infinite-layer nickelates, transition temperature can be enhanced via only ~ 1% compressive strain-tuning with root of enhancement still being elusive. Using resonant inelastic x-ray scattering (RIXS), we investigate magnetic excitations in PrNiO
The fundamental optical excitations of correlated transition-metal compounds are typically identified with multielectronic transitions localized at the site, such as <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>d</a:mi><a:mi>d</a:mi></a:math> transitions. In this vein, intense interest has surrounded appearance sharp, below-band-gap transitions, i.e., excitons, within magnetic phase <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"...
Nickelates are known for their metal to insulator transition (MIT) and an unusual magnetic ordering, occurring at T = TNéel. Here, we investigate thin films of SmNiO3 subjected different levels epitaxial strain. We find that the original bulk behavior (TNéel < TMI) is strongly affected by applying compressive strain films. For small strains, a regime where TNéel TMI achieved, paramagnetic insulating phase characteristic compound suppressed MIT becomes 1st order. Further increasing in-plane...
We present the optical design of Centurion soft X-ray resonant inelastic scattering (RIXS) spectrometer to be located on SIX beamline at NSLS-II. The is designed reach a resolving power 100 000 1000 eV its best resolution. It also have continuously variable 2θ motion over range 112° using custom triple rotating flange. analyzed several possible designs capable reaching target After careful analysis, we adopted Hettrick-Underwood design, with an additional plane mirror maintain fixed...
Bulk NdNiO_3 and thin films grown along the pseudocubic (001)_pc axis display a 1st order metal to insulator transition (MIT) together with N\'eel at T=200K. Here, we show that for NdNiO3 deposited on (111)_pc NdGaO_3 MIT occurs T=335K T=230 K. By comparing transport magnetic properties of layers substrates different symmetries lattice parameters, demonstrate particularly large tuning when epitaxy is realized surfaces. We attribute this effect specific matching conditions imposed direction...
Abstract The sustained interest in investigating magnetism the 2D limit of insulating antiferromagnets is driven by possibilities discovering, or engineering, novel magnetic phases through layer stacking. However, due to difficulty directly measuring interactions antiferromagnets, it not yet understood how intra , strongly correlated, materials can be modified proximity. Herein, impact reduced dimensionality model van der Waals antiferromagnet NiPS 3 explored electronic excitations...
Single-photon emitters serve as building blocks for many emerging concepts in quantum photonics. The recent identification of bright, tunable, and stable hexagonal boron nitride (hBN) has opened the door to platforms operating across infrared ultraviolet spectrum. While it is widely acknowledged that defects are responsible single-photon hBN, crucial details regarding their origin, electronic levels, orbital involvement remain unknown. Here, we employ a combination resonant inelastic X-ray...
We have performed x-ray linear and circular magnetic dichroism experiments at the $\text{Mn}\text{ }{L}_{2,3}$ edge of ${\text{La}}_{0.7}{\text{Sr}}_{0.3}{\text{MnO}}_{3}$ ultrathin films. Our measurements show that antiferromagnetic (AF) insulating phase is stabilized by interfacial rearrangement }3d$ orbitals, despite relevant magnetostriction anisotropic effect on double-exchange ferromagnetic (FM) metallic phase. As a consequence, Mn atomic magnetic-moment orientation how it reacts to...
Recently it was predicted theoretically and confirmed experimentally that in cuprates single-magnon dispersions can be mapped out with resonant inelastic x-ray scattering (RIXS) at the copper ${L}_{3}$ edge. To further establish RIXS as a viable technique we investigate momentum incident photon polarization dependence of spectral weight variety layered undoped antiferromagnetic compounds. The agreement experimental theoretical results bolsters assignment features to single magnons. This...
We assess the capabilities of magnetic Resonant Inelastic X-ray Scattering (RIXS) at O $K$ edge in undoped cuprates by taking La_{2}CuO_{4} as a benchmark case, based on series RIXS measurements that we present here. By combining experimental results with basic theory point out fingerprints bimagnon spectra. These are dominant peak around 450 meV, almost complete absence dispersion both $\pi$ and $\sigma$ polarization constant intensity vs. transferred momentum polarization. This behavior is...
Abstract Strongly correlated insulators are broadly divided into two classes: Mott–Hubbard insulators, where the insulating gap is driven by Coulomb repulsion U on transition-metal cation, and charge-transfer energy Δ between cation ligand anions. The relative magnitudes of determine which class a material belongs to, subsequently nature its low-energy excitations. These scales typically understood through local chemistry active ions. Here we show that situation more complex in...
The discovery of charge-density-wave-related effects in the resonant inelastic x-ray scattering spectra cuprates holds tantalizing promise clarifying interactions that stabilize electronic order. Here, we report a comprehensive study ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ finding charge-density wave persist up to remarkably high doping level $x=0.21$ before disappearing at $x=0.25$. excitation remain essentially unchanged with despite crossing topological...
Perovskite nickelates possess an intimate connection among the structural, electronic, and magnetic orders. We investigate how crystal-field disorder induced by cation size variance impacts emergence of macroscopic magnetic, electronic behaviors in single crystal high-entropy oxide nickelate films. The degree variation sizes hosted on lattice is found to strongly influence critical ordering temperatures. Resonant x-ray scattering density functional theory describe high-variance systems...
The electronic structure of Cu-doped ZnO thin films, synthesized with a nominal composition Zn1−xCuxO (x=0.03, 0.05, 0.07, and 0.10) by using spray pyrolysis method, has been investigated near-edge x-ray absorption fine (NEXAFS) experiments at the O K- Cu L3,2-edges resonant inelastic scattering (RIXS) measurements L3,2 edge. films showed single phase wurtzite-hexagonal like crystal ferromagnetic behavior room temperature (RT). intensity pre-edge spectral feature K-edge increases...
The magnetic and electronic modifications induced at the interfaces in ${({\text{SrMnO}}_{3})}_{n}/{({\text{LaMnO}}_{3})}_{2n}$ superlattices have been investigated by linear circular dichroism $\text{Mn}\text{ }{L}_{2,3}$ x-ray absorption spectra. Together with theoretical calculations, our data demonstrate that charge redistribution across favors in-plane ferromagnetic (FM) order ${e}_{g}({x}^{2}\ensuremath{-}{y}^{2})$ orbital occupation, agreement average strain. Far from interfaces,...