A5101692369- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Particle physics theoretical and experimental studies
- Quantum Chromodynamics and Particle Interactions
- High-Energy Particle Collisions Research
- Rare-earth and actinide compounds
- High-pressure geophysics and materials
- Multiferroics and related materials
- Iron-based superconductors research
- Theoretical and Computational Physics
- X-ray Diffraction in Crystallography
- Hip disorders and treatments
- Magnetic properties of thin films
- Perovskite Materials and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Orthopaedic implants and arthroplasty
- Topological Materials and Phenomena
- Electronic and Structural Properties of Oxides
- Dark Matter and Cosmic Phenomena
- Particle Accelerators and Free-Electron Lasers
- Magnetism in coordination complexes
- Fuel Cells and Related Materials
- Electron and X-Ray Spectroscopy Techniques
- Magnetic Properties of Alloys
University of Toronto
2016-2025
Boston Children's Hospital
2005-2024
Kyungpook National University Hospital
2024
Indiana University – Purdue University Indianapolis
1999-2019
Indiana University School of Medicine
1999-2019
Harvard University
1995-2018
Korea University
2018
Korea Institute of Science & Technology Information
2011-2017
Kyungpook National University
2004-2016
Seoul National University
1994-2016
Systematic low-energy neutron-scattering studies have been performed on float-zone-grown single crystals of ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ with $x$ extending from zero doping, $x=0$, to the overdoped, weakly superconducting regime, $x=0.25$. For beyond a critical doping value ${x}_{c}\ensuremath{\approx}0.05$ spin-fluctuation peak position shifts ($\frac{1}{2}$, $\frac{1}{2}$) ($\frac{1}{2}$\ifmmode\pm\else\textpm\fi{}\ensuremath{\delta},...
We examine the role of spin-orbit coupling in electronic structure $\ensuremath{\alpha}\ensuremath{-}{\mathrm{RuCl}}_{3}$, which Ru ions $4{d}^{5}$ configuration form a honeycomb lattice. Our x-ray absorption spectroscopy measurements at $L$ edges exhibit distinct spectral features associated with presence substantial coupling, as well an anomalously large branching ratio. Furthermore measured optical spectra can be described very first-principles calculations obtained by taking into account...
We used resonant inelastic x-ray scattering to reveal the nature of magnetic interactions in Sr2IrO4, a 5d transition-metal oxide with spin-orbit entangled ground state and Jeff=1/2 momemts, referred as 'isospins'. The magnon dispersion Sr2IrO4 is well described by an antiferromagnetic Heisenberg model isospin one-half moments on square lattice, which renders low-energy effective physics much akin that superconducting cuprates. This further supported observation exciton modes whose strongly...
We report magnetic and thermodynamic properties of single crystal $\ensuremath{\alpha}\ensuremath{-}{\text{RuCl}}_{3}$, in which the ${\text{Ru}}^{3+}\phantom{\rule{0.28em}{0ex}}(4{d}^{5})$ ion is its low spin state forms a honeycomb lattice. Two features are observed both susceptibility specific heat data; sharp peak at 7 K broad hump near 10--15 K. In addition, we observe metamagnetic transition between 5 10 T. Our neutron diffraction study samples confirms that temperature associated with...
The combination of electronic correlation and spin-orbit coupling is thought to precipitate a variety highly unusual phases in solids, including topological quantum spin liquid states. We report Raman scattering study that provides evidence for unconventional excitations α-RuCl_{3}, coupled Mott insulator on the honeycomb lattice. In particular, our measurements reveal magnetic scattering, typified by broad continuum. temperature dependence this continuum evident over large scale compared...
We report a combined experimental and theoretical investigation of the magnetic structure honeycomb lattice magnet Na$_2$IrO$_3$, strong candidate for realization gapless spin-liquid. Using resonant x-ray scattering at Ir L$_3$-edge, we find 3D long range antiferromagnetic order below T$_N$=13.3 K. From azimuthal dependence Bragg peak, ordered moment is determined to be predominantly along {\it a}-axis. Combining data with first principles calculations, propose that most likely spin novel...
The electronic structure of the honeycomb lattice iridates ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$ and ${\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}$ has been investigated using resonant inelastic x-ray scattering (RIXS). Crystal-field-split $d\mathrm{\text{\ensuremath{-}}}d$ excitations are resolved in high-resolution RIXS spectra. In particular, splitting due to noncubic crystal fields, derived from ${j}_{\mathrm{eff}}=3/2$ states, is much smaller than typical spin-orbit energy scale iridates,...
We have performed x-ray absorption spectroscopy (XAS) measurements on a series of Ir-based 5$d$ transition metal compounds, including Ir, IrCl${}_{3}$, IrO${}_{2}$, Na${}_{2}$IrO${}_{3}$, Sr${}_{2}$IrO${}_{4}$, and Y${}_{2}$Ir${}_{2}$O${}_{7}$. By comparing the intensity ``white-line'' features observed at Ir L${}_{2}$ L${}_{3}$ edges, it is possible to extract valuable information about strength spin-orbit coupling in these systems. observe remarkably large, nonstatistical branching ratios...
The low-temperature magnetic phases in the layered honeycomb lattice material $\alpha$-RuCl$_3$ have been studied as a function of in-plane field. In zero field this orders magnetically below 7 K with so-called zigzag order within planes. Neutron diffraction data show that relatively small applied 2 T is sufficient to suppress population domain which chains run along direction. We found intensity peaks due continuously suppressed increasing until their disappearance at $\mu_o$H$_c$=8 T. At...
The honeycomb Kitaev-Heisenberg model is a source of quantum spin liquid with Majorana fermions and gauge flux excitations as fractional quasiparticles. Here we unveil the highly unusual low-temperature heat conductivity $\ensuremath{\kappa}$ $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$, prime candidate for realizing such physics: beyond magnetic field ${B}_{c}\ensuremath{\approx}7.5\text{ }\text{ }\mathrm{T}$, increases by about one order magnitude, both in-plane well...
Angle-resolved photoemission studies on ${\mathrm{Sr}}_{2}{\mathrm{CuO}}_{2}{\mathrm{Cl}}_{2}$ at a temperature below its N\'eel reveal detailed momentum dependent line shape changes as function of wave vector. While sharp quasiparticlelike peak is observed near ( $\ensuremath{\pi}/2,\ensuremath{\pi}/2$), broad peaks are $\ensuremath{\pi},0$). Additional second and third neighbor hopping terms must be added to the $t\ensuremath{-}J$ Hamiltonian account for both dispersion shape. It found...
We demonstrate a method of x-ray absorption spectroscopy (XAS) that is bulk sensitive, like traditional fluorescence yield measurements, but not affected by self-absorption or saturation effects. This measure XAS achieved scanning the incident photon energy through an edge and using energy-sensitive detector to partial (PFY). The emission from any element core-hole excitation resonant with under investigation selected PFY. It found inverse this PFY spectrum, which we term (IPFY), linearly...
We present the results of an amplitude analysis anti-B0 -> J/psi K- pi+ decays. A new charged charmoniumlike state Zc(4200)+ decaying to is observed with a significance 6.2 sigma. The mass and width are 4196 +31-29 +17-13 MeV/c^2 370 +70-70 +70-132 MeV, respectively; preferred assignment quantum numbers J^P = 1^+. In addition, we find evidence for Zc(4430)+ pi+. based on 711 fb^-1 data sample collected by Belle detector at asymmetric-energy e+ e- collider KEKB.
Mott insulators with strong spin-orbit coupling have been proposed to host unconventional magnetic states, including the Kitaev quantum spin liquid. The 4$d$ system $\alpha$-RuCl$_3$ has recently come into view as a candidate system, evidence for unusual excitations in scattering experiments. We apply combination of optical spectroscopy and Raman study electronic structure this material. Our measurements reveal series orbital involving localized total angular momentum states Ru ion, implying...
We report the first observations of spin-singlet bottomonium states hb(1P) and hb(2P). The are produced in reaction e+e−→hb(nP)π+π− using a 121.4 fb−1 data sample collected at energies near Υ(5S) resonance with Belle detector KEKB asymmetric-energy e+e− collider. determine M[hb(1P)]=(9898.2+1.1+1.0−1.0−1.1) MeV/c2 M[hb(2P)]=(10 259.8±0.6+1.4−1.0) MeV/c2, which correspond to P-wave hyperfine splittings ΔMHF=(+1.7±1.5) (+0.5+1.6−1.2) respectively. significances hb(2P) 5.5σ 11.2σ, find that...
We report a study of $B\to (J/\psi \gamma) K$ and (\psi' \gamma)K$ decay modes using $772\times 10^{6}$ $B\bar{B}$ events collected at the \Upsilon(4S)$ resonance with Belle detector KEKB energy-asymmetric $e^+ e^-$ collider. observe $X(3872) \to J/\psi \gamma$ first evidence for $\chi_{c2} in (X_{c\bar{c}}\gamma) decays, while search \psi' no significant signal is found. measure branching fractions, $\mathcal{B}(B^{\pm} X(3872) K^{\pm}) \mathcal{B}(X(3872) J/\psi\gamma)$ $=$...
We report on a search for heavy neutrinos in B-meson decays. The results are obtained using data sample that contains 772x10^6 BB-bar pairs collected at the Upsilon(4S) resonance with Belle detector KEKB asymmetric-energy e+e- collider. No signal is observed and upper limits set mixing of left-handed Standard Model mass range 0.5 - 5.0 GeV/c^2.
We report a Fe K$\ensuremath{\beta}$ x-ray emission spectroscopy study of local magnetic moments in various iron-based superconductors their paramagnetic phases. Local are found all samples studied: PrFeAsO, $\mathrm{Ba}{(\mathrm{Fe},\mathrm{Co})}_{2}{\mathrm{As}}_{2}$, LiFeAs, Fe${}_{1+x}$(Te,Se), and ${\mathrm{A}}_{2}{\mathrm{Fe}}_{4}{\mathrm{Se}}_{5}$ (where $\text{A}=\text{K}$, Rb, Cs). The moment size is independent temperature or carrier concentration but varies significantly across...
Experiments show that magnons in CoTiO${}_{3}$ have a similar energy-momentum relation to electrons graphene, setting up as good system which study interactions between so-called Dirac bosons.
The material $\alpha$-RuCl$_3$ has been the subject of intense scrutiny as a potential Kitaev quantum spin liquid, predicted to display Majorana fermions low energy excitations. In practice, undergoes transition state with antiferromagnetic order below temperature $T_{\rm N}$ $\approx$ 7 K, but this can be suppressed by applying an external in-plane magnetic field $H_\parallel$ = T. Whether liquid phase exists just above that is still open question, reported observation quantized thermal...
The 2D layered insulator $\alpha$-RuCl$_3$ is a candidate material for quantum spin-liquid state, which may be realized when magnetic field suppresses the antiferromagnetic order present at low temperature. Oscillations in dependence of thermal conductivity, observed an in-plane $B$ up to critical $B^{\star}$, have been attributed exotic charge-neutral fermions, viewed as evidence state between $B_{c}$ $\simeq 7$ T phase ends and $B^{\star}$. Here we report measurements conductivity function...
Utilizing resonant inelastic x-ray scattering, we report a previously unobserved mode in the excitation spectrum of ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ and ${\mathrm{Nd}}_{2}{\mathrm{CuO}}_{4}$ at 500 meV. The is peaked around ($\ensuremath{\pi}$, 0) point reciprocal space observed to soften, broaden, away from this point. Samples with $x=0$, 0.01, 0.05, 0.17 were studied. new found be rapidly suppressed increasing Sr content absent $x=0.17$, where it...
The nuclear localization and phosphorylation of three 25-kilodalton rat myoblast stress proteins were examined. Data obtained in these analyses led to the following conclusions: (i) all become localized nucleus stressed cells, (ii) two are modified by phosphorylation, (iii) occurs exclusively on serine residues.