A5057764061- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Iron-based superconductors research
- Topological Materials and Phenomena
- Graphene research and applications
- Electronic and Structural Properties of Oxides
- Intellectual Capital and Performance Analysis
- Quantum and electron transport phenomena
- Advancements in Photolithography Techniques
- Magnetic properties of thin films
- Rare-earth and actinide compounds
- 3D IC and TSV technologies
- Semiconductor materials and devices
- Chemical and Physical Properties of Materials
- Corporate Taxation and Avoidance
Samsung (South Korea)
2023
Seoul National University
2018-2022
Institute for Basic Science
2018-2022
We utilize near-infrared femtosecond pulses to investigate coherent phonon oscillations of Ca2RuO4. The Ag mode the lowest frequency changes abruptly not only its amplitude but also oscillation-phase as spin order develops. In addition, shows a redshift entering magnetically ordered state, which indicates spin-phonon coupling in system. Density functional theory calculations reveal that result octahedral tilting distortions, are exactly sync with lattice deformation driven by magnetic...
We employ an optical pump-probe technique to study coherent phonon oscillations in ${\mathrm{Ca}}_{2}{\mathrm{RuO}}_{4}$. find that oscillation amplitude of ${A}_{g}$ symmetric mode is strongly suppressed at 260 K, a putative transition point orbital ordering. The also shows gradual but huge change its phase, such the even flips over with ${180}^{\ensuremath{\circ}}$ across temperature. Density functional theory calculations indicate has eigenmode octahedral distortion conventional tilting...
We investigate the ultrafast dynamics of Cd$_2$Os$_2$O$_7$, a prototype material showing Lifshitz-type transition as function temperature. In paramagnetic metallic state, photo-reflectivity shows sub-picosecond relaxation, followed by featureless small offset. antiferromagnetic state slightly below $T_N$, however, resurges over hundreds picoseconds, which goes beyond usual realm effective-temperature model. Our observations are consistent with Lifshitz phase Cd$_2$Os$_2$O$_7$ driven...
We investigate ultrafast dynamics from photoinduced reflectivity of Sr2RhO4 by using femtosecond near-infrared pulses. observe a clear temperature-dependent anomaly in its electronic which slows down below 160 K. In addition, coherent oscillations the A1g symmetric 5.3-THz phonon exhibit 90-degree shift initial phase across TS, indicating structural change octahedral rotation distortions. propose that structure evolves at around and it can influence on non-equilibrium carriers as well...
Photoexcited carriers in three-dimensional topological insulators (3D TIs) decay rapidly through the electron-electron and electron-phonon scattering. While most studies focus on such fast dynamics, recent experiments find slow photovoltage (PV) dynamics arising from band-bending potentials, which optical transitions two-dimensional electron gas (2DEG) are effective. Although early investigations speculated existence of multiple structures TI surface to bulk, how PV 2DEG correlated presence...
The photoinduced reflectivity change of optimally doped BaFe 1.87 Co 0.13 As 2 is investigated. It observed that the nematic signal in continues to increase as temperature decreases, reflecting its fluctuating nature. However, fluence‐dependent measurements show saturation at higher pump fluence, a typical behavior static order parameter. Temperature‐dependent evolution and characteristic relaxation time suggest nematicity spin and/or orbital origin develops lower on top coupled lattice...
In this paper the use of EPE metric directly in process optimization method for a DRAM case has been researched. We show that EPE-aware optimization, using scanner dose and overlay control sub-recipes, is outperforming conventional terms Dies Spec. Hence, it can be expected also device yield improved by control.
We investigate coherent phonon oscillations of ${\mathrm{BaFe}}_{2}{\mathrm{As}}_{2}$ using optical pump-probe spectroscopy. Time-resolved reflectivity shows periodic modulations due to the ${A}_{1g}$ $c$-axis arsenic vibrations. Optical probe beams polarized along orthorhombic $a$ and $b$ axes reveal that initial phase a systematic deviation as function temperature, although these arise from same The oscillation remains anisotropic even in tetragonal structure, reflecting nematic response...
We present a strain-dependent time-resolved reflectometry experiment on $\mathrm{Ba}{({\mathrm{Fe}}_{0.955}{\mathrm{Co}}_{0.045})}_{2}{\mathrm{As}}_{2}$ in the nematic state. Uniaxial external pressure has usually been applied to obtain single domain. However, reflectivity with and without pumping under uniaxial strain along ${[110]}_{\text{tetr}}$ reveals an unexpected nematicity of which ${C}_{4}$ symmetry-breaking orientation is rotated by ${20}^{\ensuremath{\circ}}$. Our observation...
Electronic nematicity have attracted a great deal of interest in the unconventional superconductivity research. We present an experimental method to investigate reflectivity anisotropy by electronic and its non-equilibrium dynamics. Our results on Ba(Fe$_{0.955}$Co$_{0.045}$)$_{2}$As$_{2}$ single crystal clearly feature broken four-fold symmetry along directions parallel Fe-Fe bonding. Numerical simulations using WVASE from Woollam Co. demonstrate that our is highly reliable under various...
High surface-mobility, which is attributable to topological protection, a trademark of three-dimensional insulators (3DTIs). Exploiting surface-mobility indicates successful application properties for practical purposes. However, the detection has been hindered by inevitable bulk conduction. Even in case high-quality crystals, state forms dominant channel electrical current. Therefore, with transport measurement, can be resolved only below-micrometer-thick crystals. The evaluation becomes...