Showing papers by "Shik Shin published in 2022"
TL;DR: In this article , using 7-eV laser-based angle-resolved photoemission spectroscopy and Eliashberg function analysis, the authors determined an intermediate λ=0.45 −0.6 at T = 6 K for both Sb 5 p and V 3 d electronic bands, which can support a conventional superconducting transition temperature on the same magnitude of experimental value.
Abstract: Abstract In crystalline materials, electron-phonon coupling (EPC) is a ubiquitous many-body interaction that drives conventional Bardeen-Cooper-Schrieffer superconductivity. Recently, in a new kagome metal CsV 3 Sb 5 , superconductivity that possibly intertwines with time-reversal and spatial symmetry-breaking orders is observed. Density functional theory calculations predicted weak EPC strength, λ, supporting an unconventional pairing mechanism in CsV 3 Sb 5 . However, experimental determination of λ is still missing, hindering a microscopic understanding of the intertwined ground state of CsV 3 Sb 5 . Here, using 7-eV laser-based angle-resolved photoemission spectroscopy and Eliashberg function analysis, we determine an intermediate λ=0.45–0.6 at T = 6 K for both Sb 5 p and V 3 d electronic bands, which can support a conventional superconducting transition temperature on the same magnitude of experimental value in CsV 3 Sb 5 . Remarkably, the EPC on the V 3 d -band enhances to λ~0.75 as the superconducting transition temperature elevated to 4.4 K in Cs(V 0.93 Nb 0.07 ) 3 Sb 5 . Our results provide an important clue to understand the pairing mechanism in the kagome superconductor CsV 3 Sb 5 .
8 citations
TL;DR: The spin-dependent band structure of CoS 2 , which is a candidate for a half-metallic ferromagnet, was investigated by both spin- and angle-resolved photoemission spectroscopy and theoretical calculations to reappraise the halfmetallicity and electronic correlations as discussed by the authors .
Abstract: The spin-dependent band structure of CoS 2 , which is a candidate for a half-metallic ferromagnet, was investigated by both spin- and angle-resolved photoemission spectroscopy and theoretical calculations to reappraise the half-metallicity and electronic correlations. We determined the three-dimensional Fermi surface and the spin-dependent band structure. As a result, we found that a part of the minority spin bands is on the occupied side in the vicinity of the Fermi level, providing spectroscopic evidence that CoS 2 is not a half-metal but very close. Band calculations using density functional theory with generalized gradient approximation showed good agreement with the observed majority spin e g bands, while it could not explain the observed band width of the minority-spin e g bands. On the other hand, theoretical calculations using dynamical mean field theory could better reproduce the strong mass renormalization in the minority-spin e g bands. Our results strongly suggest the presence of anomalously enhanced spin-dependent electron correlation effects on the electronic structure in the vicinity of the half-metallic state. We also report the temperature dependence of the electronic structure across the Curie temperature and discuss the mechanism of the thermal demagnetization. Our discovery of the anomalously large spin-dependent electronic correlations not only demonstrates a key factor in understanding the electronic structure of half-metals but also provides a motivation to improve theoretical calculations on spin-polarized strongly correlated systems.
3 citations
TL;DR: In this article , the authors investigated the nonequilibrium electronic structure of 1 T -TaS 2 by time and angle-resolved photoemission spectroscopy, and they observed that strong photo excitation induces collapse of the Mott gap, leading to the photo-induced metallic phase.
Abstract: We investigate the nonequilibrium electronic structure of 1 T -TaS 2 by time- and angle-resolved photoemission spectroscopy. We observe that strong photo excitation induces collapse of the Mott gap, leading to the photo-induced metallic phase. It is also found that the oscillation of photoemission intensity occurs as a result of the excitations of coherent phonons corresponding to the amplitude mode of the charge density wave (CDW). To study the dynamical change of the band dispersions modulated by the CDW amplitude mode, we perform analyses by using frequency-domain angle-resolved photoemission spectroscopy. We find that two different peak structures exhibit anti-phase oscillation with respect to each other. They are attributed to the minimum and maximum band positions in energy, where the single band is oscillating between them synchronizing with the CDW amplitude mode. We further find that the flat band constructed as a result of CDW band folding survive with the collapse of Mott gap. Our results strongly suggest the CDW phase is more robust than the Mott insulating phase, and the lattice modulation corresponding to the CDW amplitude mode dynamically modulate the Mott gap.
1 citations
TL;DR: In this article , high-resolution angle-resolved photoemission spectroscopy (ARPES) and spin-resolution ARPES are applied to investigate the electronic and spin structure of the topological surface states (TSS) in the superconducting 2M-WS2.
Abstract: The quantum spin Hall (QSH) effect has attracted extensive research interest because of the potential applications in spintronics and quantum computing, which is attributable to two conducting edge channels with opposite spin polarization and the quantized electronic conductance of 2e2/h. Recently, 2M-WS2, a new stable phase of transition metal dichalcogenides with a 2M structure showing a layer configuration identical to that of the monolayer 1T' TMDs, was suggested to be a QSH insulator as well as a superconductor with a critical transition temperature of around 8 K. Here, high-resolution angle-resolved photoemission spectroscopy (ARPES) and spin-resolved ARPES are applied to investigate the electronic and spin structure of the topological surface states (TSS) in the superconducting 2M-WS2. The TSS exhibit characteristic spin-momentum-locking behavior, suggesting the existence of long-sought nontrivial Z2 topological states therein. We expect that 2M-WS2 with coexisting superconductivity and TSS might host the promising Majorana bound states.
1 citations
TL;DR: In this paper , the growth process and structure of a hydrogen-bonded organic framework (HOF) using low-energy electron diffraction and X-ray photoemission spectroscopy is revealed.
Abstract: Molecular adsorption on noble‐metal surfaces influences the Rashba effect in the Shockley surface state (SS), but the underlying mechanism remains unclear. Melamine is a simple molecule with a symmetric backbone consisting of a heterocyclic ring. It self‐assembles into a rosette‐like superstructures on Au(111) via double intermolecular hydrogen bonds. In this study, the growth process and structure of this hydrogen‐bonded organic framework (HOF) using low‐energy electron diffraction and X‐ray photoemission spectroscopy is revealed. Above room temperature, it is impossible for melamine to be adsorbed on Au(111) as a monomer, but it is adsorbed collectively as a hydrogen‐bonding network. The melamine HOF has a characteristic hexagonal honeycomb structure (MHC), which significantly affects both the structure and electronic states of Au(111). A theoretical approach reveals that MHC induces a hexagonal periodic deformation in the structure of Au(111) and introduces a new periodic potential in the surface electronic system. Angle‐resolved photoemission spectroscopy measurements of MHC/Au(111) indicate that the bulk sp band is strongly folded back, enhancing the Rashba splitting of the SS of Au(111). Furthermore, spin‐ and angle‐resolved photoemission spectroscopy reveals that the enhanced Rashba splitting of the SS by the MHC is the largest reported to date for the adsorption system on Au(111).
1 citations
TL;DR: In this paper , a technique using a teeth supported dental implant guide to reconstruct proper occlusion immediately after tumor ablation was reported, which dramatically shortens period of dentition loss.
TL;DR: In this article , Kouto et al. proposed a method for the detection of X-ray Spectroscopy (X-ray) spectra in the context of solid state physics.
Abstract: A. Chainani, T. Yokoya, Y. Takata, K. Tamasaku, M. Taguchi, T. Shimojima, N. Kamakura, K. Horiba, S. Tsuda, S. Shin, D. Miwa, Y. Nishino, T. Ishikawa, M. Yabashi, K. Kobayashi, H. Namatame, M. Taniguchi, K. Takada, T. Sasaki, H. Sakurai, and E. Takayama-Muromachi. Soft X-ray Spectroscopy Lab, RIKEN/SPring-8, 1-1-1 Kouto, Mikazuki-cho, Sayo-gun, Hyogo 679-5148, Japan Institute for Solid State Physics, University of Tokyo, Kashiwa,Chiba 277-8581, Japan Coherent X-ray Optics Lab, RIKEN/SPring-8, 1-1-1 Kouto, Mikazuki-cho, Sayo-gun, Hyogo 679-5148, Japan JASRI/SPring-8, 1-1-1 Kouto, Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan HiSOR, Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima 739-8526, Japan National Institute for Materials Science, Tsukuba, Ibaraki, 305-0044, Japan and CREST, Japan Science and Technology Corporation (Dated: November 12, 2018)
02 Dec 2022
TL;DR: In this article , the authors propose a solution to solve the problem of the problem: this article ] of "uniformity" and "uncertainty" of the solution.
Abstract: ,
TL;DR: A. Horiba et al. as mentioned in this paper proposed a method for X-ray Spectroscopy Spectral Spectroglobalization (SDS) and showed that SDS can be used to obtain a more accurate X-Ray Spectrographic Spectrogram (XRS) image.
Abstract: K. Horiba, ∗ M. Taguchi, A. Chainani, Y. Takata, E. Ikenaga, D. Miwa, Y. Nishino, K. Tamasaku, M. Awaji, A. Takeuchi, M. Yabashi, H. Namatame, M. Taniguchi, H. Kumigashira, M. Oshima, M. Lippmaa, M. Kawasaki, H. Koinuma, K. Kobayashi, T. Ishikawa, and S. Shin 6 Soft X-Ray Spectroscopy Laboratory, RIKEN/SPring-8, Mikazuki-cho, Hyogo 679-5148, Japan JASRI/SPring-8, Mikazuki-cho, Hyogo 679-5198, Japan Coherent X-Ray Optics Laboratory, RIKEN/SPring-8, Mikazuki-cho, Hyogo 679-5148, Japan HiSOR, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577, Japan Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan (Dated: March 22, 2022)
TL;DR: In this article , the authors investigated the nonequilibrium electronic structure of 1T-TaS2 by time and angle-resolved photoemission spectroscopy and found that strong photoexcitation induces the collapse of the Mott gap, leading to the photoinduced metallic phase.
Abstract: We investigate the nonequilibrium electronic structure of 1T-TaS2 by time- and angle-resolved photoemission spectroscopy. We observe that strong photoexcitation induces the collapse of the Mott gap, leading to the photo-induced metallic phase. It is also found that the oscillation of photoemission intensity occurs as a result of the excitations of coherent phonons corresponding to the amplitude mode of the charge density wave (CDW). To study the dynamical change in the band dispersions modulated by the CDW amplitude mode, we perform analyses by using frequency-domain angle-resolved photoemission spectroscopy (FDARPES). We find that two different peak structures exhibit anti-phase oscillation with respect to each other by retrieving the amplitude and phase parts of the FDARPES spectra. They are attributed to the minimum and maximum band positions in energy, where the single band is oscillating between them synchronizing with the CDW amplitude mode. We further find that the flatband constructed as a result of CDW band folding survives during the oscillation while the Mott gap is significantly reduced. Our results suggest the CDW phase is robust, and the lattice modulation corresponding to the CDW amplitude mode dynamically modulates the Mott gap.
TL;DR: In this article , a combination of time and angle-resolved photoemission spectroscopy (tr-ARPES) and ultrafast timeresolved terahertz (trTHz) spectra was employed to investigate the photovoltage and 2DEG dynamics in the prototypical topological insulator.
Abstract: 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 the slow photovoltage (PV) dynamics arising from the band-bending potentials, in which the optical transitions in two-dimensional electron gas (2DEG) are effective. Although early investigations speculated the existence of multiple band-bending structures from the TI surface to the TI bulk, how PV and 2DEG are correlated in the presence of such multiple band bendings has been less explored. Here, we employ the combination of time- and angle-resolved photoemission spectroscopy (tr-ARPES) and ultrafast time-resolved terahertz (tr-THz) spectroscopy to investigate the PV and 2DEG dynamics in the prototypical topological insulator ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$. Our tr-ARPES analysis identifies two spatially separated PV dynamics associated with two types of band bending: one is the well-known surface PV, and another PV is formed deep within the bulk, which we call ``internal bulk PV.'' For the surface PV, our tr-THz spectra substantiate that the $\ensuremath{\mu}\mathrm{s}$-long transient signal arises from the surface-PV-induced increase of the TSS and 2DEG carrier density, which appears as a transient blueshift of a Fermi cutoff and an increased ARPES intensity in the tr-ARPES measurements. In contrast, the effect of the internal bulk PV shows only marginal changes in the 2DEG and TSS carrier densities but shifts the entire binding energy of the near-surface bands.