A5074537573- Physics of Superconductivity and Magnetism
- Iron-based superconductors research
- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Magnetic properties of thin films
- Quantum and electron transport phenomena
- Graphene research and applications
- Carbon Nanotubes in Composites
- Surface and Thin Film Phenomena
- Dark Matter and Cosmic Phenomena
- Rare-earth and actinide compounds
- Corporate Taxation and Avoidance
- Superconducting Materials and Applications
- Superconductivity in MgB2 and Alloys
- Advanced Electrical Measurement Techniques
- Electronic and Structural Properties of Oxides
- Particle physics theoretical and experimental studies
- Intellectual Capital and Performance Analysis
- Force Microscopy Techniques and Applications
- Advanced Chemical Physics Studies
- Sensor Technology and Measurement Systems
- Molecular Junctions and Nanostructures
- Advanced Materials Characterization Techniques
- Atomic and Subatomic Physics Research
- Image and Signal Denoising Methods
Institute for Basic Science
2019-2024
Seoul National University
1997-2023
Seoul National University Hospital
2023
Korea Advanced Institute of Science and Technology
2012-2022
Cornell University
1999-2017
Korea University
2013
Pohang University of Science and Technology
2004
Norwegian Cancer Society
2004
Purdue University West Lafayette
2001
The doping dependence of nanoscale electronic structure in superconducting Bi(2)Sr(2)CaCu(2)O(8 + delta) is studied by scanning tunneling microscopy. At all dopings, the low energy density-of-states modulations are analyzed according to a simple model quasiparticle interference and found be consistent with Fermi-arc superconductivity. coherence peaks, ubiquitous near-optimal spectra, destroyed strong underdoping new spectral type appears. Exclusively regions exhibiting this spectrum, we find...
The CAST-CAPP axion haloscope, operating at CERN inside the CAST dipole magnet, has searched for axions in 19.74 $\mu$eV to 22.47 mass range. detection concept follows Sikivie haloscope principle, where Dark Matter convert into photons within a resonator immersed magnetic field. is an array of four individual rectangular cavities inserted strong phase-matched maximize sensitivity. Here we report on data acquired 4124 h from 2019 2021. Each cavity equipped with fast frequency tuning mechanism...
A possible explanation for the existence of cuprate "pseudogap" state is that it a d-wave superconductor without quantum phase rigidity. Transport and thermodynamic studies provide compelling evidence supports this proposal, but few spectroscopic explorations have been made. One signature superconductivity particle-hole symmetric "octet" dispersive Bogoliubov quasiparticle interference modulations. Here we report on octet's evolution from low temperatures to well into underdoped pseudogap...
The electronic structure of WTe${}_{2}$ and orthorhombic $\ensuremath{\gamma}$-MoTe${}_{2}$ are theoretically claimed to contain pairs Weyl type-II points associated with linearly touching electron hole pockets. A series recent angle-resolved photoemission spectroscopy (ARPES) experiments claims observe general agreement these predictions. Here, the authors report a de Haas--van Alphen study on which, in contrast ARPES predictions, finds simpler more isotropic Fermi surface. Upon guidance...
We present the first measurement of D*(+) width using 9/fb e(+)e(-) data collected near Upsilon(4S) resonance by CLEO II.V detector. Our method uses advanced tracking techniques and a reconstruction that takes advantage small vertical size Cornell Electron-positron Storage Ring beam spot to measure energy release distribution from D*(+)-->D(0)pi(+) decay. find gamma(D*(+)) = 96+/-4 (stat)+/-22 (syst) keV. also in decay compute Delta m identical with m(D*(+))-m(D(0)) 145.412+/-0.002...
We report scanning tunneling microscopy of semiconductor-semiconductor carbon nanotube junctions with different band gaps. Characteristic features the wave functions at energy levels, such as a localized defect state, are clearly exhibited in atomically resolved spectroscopy. The peaks Van Hove singularity on each side penetrate and decay into opposite across junction over distance $\ensuremath{\sim}2\text{ }\text{ }\mathrm{n}\mathrm{m}$. These experimental accounted for, help tight-binding...
Electronic standing waves with two different wavelengths were directly mapped near one end of a single-wall carbon nanotube as function the tip position and sample bias voltage high-resolution position-resolved scanning tunneling spectroscopy. The observed caused by separate spin charge bosonic excitations are found to constitute direct evidence for Luttinger liquid. increased group velocity excitation, power-law decay their amplitudes away from scattering boundary, suppression density...
In this paper, a novel dynamical trajectory-based methodology is developed for systematically computing multiple local optimal solutions of general nonlinear programming problems with disconnected feasible components satisfying equality/inequality constraints. The proposed methodology, deterministic in nature, exploits trajectories two different systems to find solutions. consists phases: Phase I starts from an arbitrary (infeasible) initial point and finds or all the components; II adjacent...
Several paired, localized gap states were observed in semiconducting single-wall carbon nanotubes using spatially resolved scanning tunneling spectroscopy. A pair of is found far from the band edges, forming deep levels, while other located near shallow levels. With help a first-principles study, former explained by vacancy-adatom complex latter pentagon-heptagon structure. Our experimental observation indicates that presence provides means to perform local band-gap engineering as well...
In the search for axion dark matter, superconducting rf technology is important fabricating microwave cavities with high $Q$ factors, but presence of a strong external magnetic field leads to technical difficulties. This study presents polygonal design tapes high-temperature superconductor realize resonant cavity that shows no considerable degradation in fields up 8 Tesla. approach could impact engineering solutions improve dark-matter detection and other research areas requiring low loss field.
Interfacial phonons between iron-based superconductors (FeSCs) and perovskite substrates have received considerable attention due to the possibility of enhancing preexisting superconductivity. Using scanning tunneling spectroscopy, we studied correlation superconductivity $e\text{\ensuremath{-}}\text{ph}$ interaction with interfacial in an superconductor ${\mathrm{Sr}}_{2}{\mathrm{VO}}_{3}\mathrm{FeAs}$ (${T}_{c}\ensuremath{\approx}33\text{ }\text{ }\mathrm{K}$) made alternating FeSC oxide...
The high-${T}_{c}$ superconductors ${R}_{1}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ (R denotes rare-earth elements) and ${\mathrm{Y}}_{1}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ are prepared in several different processes. flowing ${\mathrm{O}}_{2}$ slowly cooled shows ${T}_{c}$=94 K, a lattice parameter ratio c/b=3.00 negative thermoelectric power S, while...
The Public Lung Database to address drug response (PLD) has been developed support research in computer aided diagnosis (CAD). Originally established for applications involving the characterization of pulmonary nodules, PLD augmented provide initial datasets CAD other diseases. In general, best performance a system is achieved when it trained with large amount well documented data. Such training databases are very expensive create and their lack general availability limits targets that can...
Host–guest interactions in porous supramolecular structures have been studied on surfaces using scanning tunneling microscopy, with anticipation of biochemical and sensor applications, but limited to cases van der Waals hydrogen bonds. Here, we the intermolecular 4,4″-dibromo-p-terphenyl molecules self-caged halogen bonds Ag(111). The caged hopped among six different configurations at higher than 50 K, showing a propeller-like pattern. At 30 they stayed one states that were stabilized...
We explore a new mechanism for switching magnetism and superconductivity in magnetically frustrated iron-based superconductor using spin-polarized scanning tunneling microscopy (SPSTM). Our SPSTM study on single-crystal Sr_{2}VO_{3}FeAs shows that current can switch the Fe-layer into nontrivial C_{4} (2×2) order, which cannot be achieved by thermal excitation with an unpolarized current. spectroscopy induced order has characteristics of plaquette antiferromagnetic Fe layer strongly...
Surface alloy formation of Fe on a Cr(100) surface was studied using UHV scanning tunneling microscope. As we deposited less than 1 ML at room temperature and subsequently annealed the substrate temperatures between 200 \ifmmode^\circ\else\textdegree\fi{}C 300 \ifmmode^\circ\else\textdegree\fi{}C, observed that atoms incorporate into surface, forming well-ordered ${\mathrm{Fe}}_{0.5}{\mathrm{Cr}}_{0.5}.$ These two elements were differentiated by imaging bias voltages near their states. The...
The closest unstable equilibrium point (UEP) method is a well-known direct of the Lyapunov type for optimally estimating stability regions nonlinear dynamical systems. One key step involved in UEP methodology computation that has lowest function value on boundary. In this paper, new computational algorithm to compute presented. proposed based homotopy-continuation combined with singular fixed-point strategy. Numerical simulation results show outperforms previously reported existing techniques.
Superconducting excitations --Bogoliubov quasiparticles -- are the quantum mechanical mixture of negatively charged electron (-e) and positively hole (+e). Depending on applied voltage bias in STM one can sample particle content such a superconducting excitation. Recent Scanning Tunneling Microscope (STM) experiments offer unique insight into inner workings state superconductors. We propose new observable quantity for studies that is manifestation particle-hole dualism quasiparticles. call...
The role of halogen bonds in self-assembled networks for systems with Br and I ligands has recently been studied scanning tunneling microscopy (STM), which provides physical insight at the atomic scale. Here, we study supramolecular interactions 1,5-dichloroanthraquinone molecules on Au(111), including Cl ligands, by using STM. Two different molecular structures chevron square are observed, their models proposed. Both stabilized intermolecular Cl⋅⋅⋅H O⋅⋅⋅H hydrogen marginal contributions...
A high Q-factor microwave resonator in a magnetic field could be used wide range of applications, especially for enhancing the scanning speed axion dark matter research. In this letter, we introduce polygon-shaped resonant cavity with commercial YBCO tapes covering entire inner wall. We demonstrated that maximum (TM$_{010}$, 6.93 GHz) superconducting was about 6 times higher than copper and showed no significant degradation up to 8 T at 4 K. This is first indication possible applications HTS...