Publications (59)
Direct Evidence for the Existence of Heavy Quasiparticles in the Magnetically Ordered Phase of CeRhIn
Masahiro Haze, Robert Peters, Yohei Torii +7
It is a long-standing important issue in heavy fermion physics whether -electrons are itinerant or localized when the magnetic order occurs. Here we report the {\it in situ} sca…
Exotic Superconducting States in FeSe-based Materials
Takasada Shibauchi, Tetsuo Hanaguri, Yuji Matsuda
High-temperature superconductivity and a wide variety of exotic superconducting states discovered in FeSe-based materials have been at the frontier of research on condensed matter…
Multiband superconductivity in the heavy fermion compound PrOs4Sb12
Gabriel Seyfarth, Jean-Pascal Brison, Marie-Aude Méasson +5
The thermal conductivity of the heavy fermion superconductor PrOs4Sb12 was measured down to Tc/40 throughout the vortex state. At lowest temperatures and for magnetic fields H ~ 0.…
Quasiparticle excitation in and around the vortex core of underdoped YBa_2Cu_4O_8 studied by site-selective NMR
K. Kakuyanagi, K. Kumagai, Yuji Matsuda
We report a site-selective ^{17}O spin-lattice relaxation rate T_1^{-1} in the vortex state of underdoped YBa_2Cu_4O_8. We found that T_1^{-1} at the planar sites exhibits an unusu…
Superconducting Gap Structure of kappa-(BEDT-TTF)2Cu(NCS)2 Probed by Thermal Conductivity Tensor
Koichi Izawa, Hidemasa Yamaguchi, Takahiko Sasaki +1
The thermal conductivity of organic superconductor kappa-(BEDT-TTF)2Cu(NCS)2 (Tc =10.4 K) has been studied in a magnetic field rotating within the 2D superconducting planes with hi…
Apparent nonreciprocal transport in FeSe bulk crystals
Taichi Terashima, Shinya Uji, Yuji Matsuda +2
We performed low-frequency ac first- and second-harmonic resistance measurements and dc measurements on bulk FeSe crystals in a temperature range between 1.8 and 150 K and in…
Nematic magnetoelastic effect contrasted between Ba(FeCo)As and FeSe
Yuwen Hu, Xiao Ren, Rui Zhang +8
To elucidate the origin of nematic order in Fe-based superconductors, we report a Raman scattering study of lattice dynamics, which quantify the extent of -symmetry breaking,…
Role of pair-breaking and phase fluctuations in c-axis tunneling in underdoped BiSrCaCuO
C. J. van der Beek, P. Spathis, S. Colson +4
The Josephson Plasma Resonance is used to study the c-axis supercurrent in the superconducting state of underdoped BiSrCaCuO with varying degrees of cont…
The interface between heavy fermions and normal electrons investigated by spatially-resolved nuclear magnetic resonance
Takayoshi Yamanaka, Masaaki Shimozawa, Ryota Endo +6
We have studied the superlattices with alternating block layers (BLs) of heavy-fermion superconductor CeCoIn5 and conventional-metal YbCoIn5 by site-selective nuclear magnetic reso…
^{31}P and ^{75}As NMR evidence for a residual density of states at zero energy in superconducting BaFe_2(As_{0.67}P_{0.33})_2
Yusuke Nakai, Tetsuya Iye, Shunsaku Kitagawa +5
^{31}P and ^{75}As NMR measurements were performed in superconducting BaFe_2(As_{0.67}P_{0.33})_2 with T_c = 30 K. The nuclear-spin-lattice relaxation rate T_1^{-1} and the Knight…
Charge Carrier Dynamics of the Heavy Fermion Metal CeCoIn Probed by THz Spectroscopy
Uwe S. Pracht, Julian Simmendinger, Martin Dressel +8
We discuss the charge carrier dynamics of the heavy-fermion compound CeCoIn in the metallic regime measured by means of quasi-optical THz spectroscopy. The transmittance of ele…
Modification of magnetic fluctuations by interfacial interactions in artificially engineered heavy-fermion superlattices
Genki Nakamine, Takayoshi Yamanaka, Shunsaku Kitagawa +7
Recent progress in the fabrication techniques of superlattices (SLs) has made it possible to sandwich several-layer-thick block layers (BLs) of heavy-fermion superconductor CeCoIn5…
Charge doping-induced quasiparticle scattering in iron-pnictide superconductors as probed by vortex pinning
Cornelis Jacominus van der Beek, Marcin Konczykowski, Shigeru Kasahara +4
Charge doping of iron-pnictide superconductors leads to collective pinning of flux vortices, whereas isovalent doping does not. Moreover, flux pinning in the charge-doped compounds…
Kitaev Quantum Spin Liquids
Yuji Matsuda, Takasada Shibauchi, Hae-Young Kee
Quantum spin liquids (QSLs) represent exotic states of matter where quantum spins interact strongly yet evade long-range magnetic order down to absolute zero. Characterized by non-…
Emergence of nontrivial magnetic excitations in a spin liquid state of kagome volborthite
Daiki Watanabe, Kaori Sugii, Masaaki Shimozawa +7
When quantum fluctuations destroy underlying long-range ordered states, novel quantum states emerge. Spin-liquid (SL) states of frustrated quantum antiferromagnets, in which highly…
Emergence of Orbital Nematicity in the Tetragonal Phase of BaFe(AsP)
Tetsuya Iye, Marc-Henri Julien, Hadrien Mayaffre +7
We report on As-NMR measurements in single crystalline BaFe(AsP) for magnetic fields parallel to the orthorhombic and $[100]_{\…
Critical current density, vortex dynamics, and phase diagram of FeSe single crystal
Yue Sun, Sunseng Pyon, Tsuyoshi Tamegai +5
We present a comprehensive study of the vortex pinning and dynamics in a high-quality FeSe single crystal, which is free from doping introduced inhomogeneities and charged quasi-pa…
Local characterization of superconductivity in BaFe2(As1-xPx)2
Yuval Lamhot, Alon Yagil, Nadav Shapira +5
We use magnetic force microscopy (MFM) to characterize superconductivity across the superconducting dome in , a pnictide with a peak in t…
Fermi surface reconstruction in FeSe under high pressure
Taichi Terashima, Naoki Kikugawa, Andhika Kiswandhi +13
We report Shubnikov-de Haas (SdH) oscillation measurements on FeSe under high pressure up to = 16.1 kbar. We find a sudden change in SdH oscillations at the onset of the pressu…
Transport evidence for twin-boundary pinning of superconducting vortices in FeSe
Taichi Terashima, Hideaki Fujii, Yoshitaka Matsushita +4
We provide bulk transport evidence for twin-boundary pinning of vortices in FeSe. We measure interlayer resistance in FeSe in magnetic fields and find that, as the field is rotated…
Se-NMR Study under Pressure on 12%-S Doped FeSe
Takanori Kuwayama, Kohei Matsuura, Yuta Mizukami +5
The 12%-S doped FeSe system has a high Tc of 30 K at a pressure of 3.0 GPa. We have successfully investigated its microscopic properties for the first time via Se-NMR measur…
Chemical Pressure and Physical Pressure in BaFe_2(As_{1-x}P_{x})_2
Lina E. Klintberg, Swee K. Goh, Shigeru Kasahara +6
Measurements of the superconducting transition temperature, T_c, under hydrostatic pressure via bulk AC susceptibility were carried out on several concentrations of phosphorous sub…
Magnetic and superconducting properties of the heavy-fermion CeCoIn5 epitaxial film probed by nuclear quadrupole resonance
Takayoshi Yamanaka, Masaaki Shimozawa, Hiroaki Shishido +6
Since the progress in the fabrication techniques of thin-films of exotic materials such as strongly correlated heavy-fermion compounds, microscopic studies of the magnetic and elec…
Magnetotransport study of the pressure-induced antiferromagnetic phase in FeSe
Taichi Terashima, Naoki Kikugawa, Shigeru Kasahara +4
The resistivity and Hall resistivity are measured on FeSe at pressures up to = 28.3 kbar in magnetic fields up to = 14.5 T. The and curves are…
Field-free superconducting diode effect in layered superconductor FeSe
Utane Nagata, Motomi Aoki, Akito Daido +7
The superconducting diode effect (SDE), where zero-resistance states appear nonreciprocally during current injection, is receiving tremendous interest in both fundamental and appli…
Resistivity and Thermal Conductivity of an Organic Insulator beta'-EtMe3Sb[Pd(dmit)2]2
Minoru Yamashita, Yuki Sato, Yuichi Kasahara +3
A finite residual linear term in the thermal conductivity at zero temperature in insulating magnets indicates the presence of gapless excitations of itinerant quasiparticles, which…
Superconducting Gap Structure of Spin-Triplet Superconductor Sr_2RuO_4 Studied by Thermal Conductivity
K. Izawa, H. Takahashi, H. Yamaguchi +7
To clarify the superconducting gap structure of the spin-triplet superconductor Sr_2RuO_4, the in-plane thermal conductivity has been measured as a function of relative orientation…
Growth of self-integrated atomic quantum wires and junctions of a Mott semiconductor
Tomoya Asaba, Lang Peng, Takahiro Ono +13
Continued advances in quantum technologies rely on producing nanometer-scale wires. Although several state-of-the-art nanolithographic technologies and bottom-up synthesis processe…
d_{x^2-y^2}- vs. d_{xy}- like pairings in organic superconductors κ-(BEDT-TTF)_2 X
Kazuhiko Kuroki, Takashi Kimura, Ryotaro Arita +2
Pairing symmetry in -(BEDT-TTF)X is re-examined by applying fluctuation exchange method to the Hubbard model on the original four band lattice for the first time. Our study…
Nature of c-axis coupling in underdoped Bi2Sr2CaCu2O8 with varying degrees of disorder
Panayotis Spathis, Sylvain Colson, Feng Yang +7
The dependence of the Josephson Plasma Resonance (JPR) frequency in heavily underdoped Bi2Sr2CaCu2O8+δon temperature and controlled pointlike disorder, introduced by high-energy e…
Decoupled nematic and magnetic criticality in FeSeS
Jake Ayres, Matija Äulo, Jonathan Buhot +7
Electronic nematicity in correlated metals often occurs alongside another instability such as magnetism. As a result, the question remains whether nematicity alone can drive unconv…
Spin fluctuations from Bogoliubov Fermi surfaces in the superconducting state of S-substituted FeSe
Zhongyu Yu, Koya Nakamura, Kazuya Inomata +9
The study of the iron-based superconductor, FeSe, has resulted in various topics, such as the interplay among superconductivity, nematicity, and magnetism, Bardeen-Cooper-Schrieffe…
Thermal-transport studies of Two-dimensional Quantum Spin Liquids
Minoru Yamashita, Takasada Shibauchi, Yuji Matsuda
Quantum spin liquids (QSLs) are fluid-like states of quantum spins where its long-range ordered state is destroyed by quantum fluctuations. The ground state of QSL and its exotic p…
Photo-induced Superconducting State with Long-lived Disproportionate Band Filling in FeSe
Takeshi Suzuki, Takashi Someya, Takahiro Hashimoto +11
Photo-excitation is a very powerful way to instantaneously drive a material into a novel quantum state without any fabrication, and variable ultrafast techniques have been develope…
Universal relationship between low-energy antiferromagnetic fluctuations and superconductivity in BaFe(AsP)
Shunsaku Kitagawa, Takeshi Kawamura, Kenji Ishida +5
To identify the key parameter for optimal superconductivity in iron pnictides, we measured the P-NMR relaxation rate on BaFe(AsP) ( and 0…
Quantum oscillations in the heat capacity of Kondo insulator YbB12
Kuan-Wen Chen, Yuan Zhu, Danilo Ratkovski +12
We observe the magnetic quantum oscillation in the heat capacity of the Kondo insulator YbB. The frequency of these oscillations T, aligns with findings from magne…
Description of resonant inelastic x-ray scattering in correlated metals
Keith Gilmore, Jonathan Pelliciari, Yaobo Huang +8
To fully capitalize on the potential and versatility of resonant inelastic x-ray scattering (RIXS), it is essential to develop the capability to interpret different RIXS contributi…
Reciprocity between local moments and collective magnetic excitations in the phase diagram of BaFe(AsP)
Jonathan Pelliciari, Kenji Ishii, Yaobo Huang +12
Unconventional superconductivity arises at the border between the strong coupling regime with local magnetic moments and the weak coupling regime with itinerant electrons, and stem…
Angular Position of Nodes in the Superconducting Gap of Quasi-2D Heavy-Fermion Superconductor CeCoIn_5
K. Izawa, H. Yamaguchi, Yuji Matsuda +3
The thermal conductivity of the heavy-fermion superconductor CeCoIn_5 has been studied in a magnetic field rotating within the 2D planes. A clear fourfold symmetry of the thermal c…
Enhancement of critical current density and mechanism of vortex pinning in H-irradiated FeSe single crystal
Yue Sun, Sunseng Pyon, Tsuyoshi Tamegai +6
In this report, we comprehensively study the effect of H irradiation on the critical current density, , and vortex pinning in FeSe single crystal. It is found that the val…
Estimation of via experiment
Keiko I. Nagao, Yuga Sakano, Takashi Shinohara +2
In this study, we conducted an experiment to estimate using body-to-body and body-to-wall collisions. By geometrically analyzing the system's motion, we first review how the c…
Pressure-induced antiferromagnetic transition and phase diagram in FeSe
Taichi Terashima, Naoki Kikugawa, Shigeru Kasahara +9
We report measurements of resistance and ac magnetic susceptibility on FeSe single crystals under high pressure up to 27.2 kbar. The structural phase transition is quickly suppress…
Charged Vortices in High Temperature Superconductors Probed by NMR
K. Kumagai, K. Nozaki, Yuji Matsuda
We report a first experimental evidence that a vortex in the high temperature superconductors (HTSC) traps a finite electric charge from the high resolution measurements of the nuc…
Quasiparticle interaction originating from Bogoliubov Fermi Surfaces under pressure in 18%-S substituted FeSe studied via NMR
Zhongyu Yu, Xiaoling Shen, Koya Nakamura +8
S-substituted FeSe superconductors in the tetragonal phase display several unique features among iron-based superconductors, particularly the presence of zero-energy excitations in…
Disorder, critical currents, and vortex pinning energies in isovalently substituted BaFe(AsP)
Sultan Demirdis, Yanina Fasano, Shigeru Kasahara +6
We present a comprehensive overview of vortex pinning in single crystals of the isovalently substituted iron-based superconductor BaFe(AsP), a material th…
In-plane and interlayer magnetoresistance in FeSe
Taichi Terashima, Shinya Uji, Hiroaki Ikeda +3
We report measurements of the in-plane and interlayer magnetoresistances of FeSe. The in-plane magnetoresistance for is positive below …
Controlling unconventional superconductivity in artificially engineered -electron Kondo superlattices
Masahiro Naritsuka, Takahito Terashima, Yuji Matsuda
Unconventional superconductivity and magnetism are intertwined on a microscopic level in a wide class of materials, including high- cuprates, iron pnictides, and heavy-fermion…
Impact of Disorder on the Superconducting Phase Diagram in BaFe(AsP)
Yuta Mizukami, Marcin Konczykowski, Kohei Matsuura +4
In many classes of unconventional superconductors, the question of whether the superconductivity is enhanced by the quantum-critical fluctuations on the verge of an ordered phase r…
Anomalous Fermi surface in FeSe seen by Shubnikov-de Haas oscillation measurements
Taichi Terashima, Naoki Kikugawa, Andhika Kiswandhi +15
We have observed Shubnikov-de Haas oscillations in FeSe. The Fermi surface deviates significantly from predictions of band-structure calculations and most likely consists of one el…
Abrupt Change of Josephson Plasma Frequency at the Phase Boundary of the Bragg Glass in Bi_2Sr_2CaCu_2O_{8+δ}
M. B. Gaifullin, Yuji Matsuda, N. Chikumoto +2
We report the first detailed and quantitative study of the Josephson coupling energy in the vortex liquid, Bragg glass and vortex glass phases of Bi_2Sr_2CaCu_2O_{8+δ} by the Jose…
Terahertz Conductivity of the Heavy-Fermion State in CeCoIn5
Marc Scheffler, Thomas Weig, Martin Dressel +5
The optical properties of thin films of the heavy-fermion compound CeCoIn5, which were deposited by molecular beam epitaxy onto MgF2 substrates, have been studied at frequencies 7…
Quasiparticle Excitations in the Superconducting State of FeSe Probed by Thermal Hall Conductivity in the Vicinity of the BCS-BEC Crossover
Tatsuya Watashige, Stevan ArsenijeviÄ, Takuya Yamashita +10
There is growing evidence that the superconducting semimetal FeSe ( K) is in the crossover regime between weak-coupling Bardeen-Cooper-Schrieffer (BCS) and strong-couplin…
From Kondo Lattices to Kondo Superlattices
Masaaki Shimozawa, Swee K. Goh, Takasada Shibauchi +1
Realizing new classes of ground states in strongly correlated electron systems continues to be at the forefront of condensed matter physics. Heavy-fermion materials, whose electron…
Hall anomaly, Quantum Oscillations and Possible Lifshitz Transitions in Kondo Insulator YbB: Evidence for Unconventional Charge Transport
Ziji Xiang, Kuan-Wen Chen, Lu Chen +10
In correlated electronic systems, strong interactions and the interplay between different degrees of freedom may give rise to anomalous charge transport properties, which can be tu…
Bulk excitations in ultraclean -RuCl: Quantitative evidence for Majorana dispersions in a Kitaev quantum spin liquid
Kumpei Imamura, Ryuichi Namba, Riku Ishioka +6
The spin-orbit coupled Mott insulator -RuCl has emerged as a prime candidate for realizing the Kitaev quantum spin liquid (KQSL), characterized by Majorana quasiparticles,…
Unusual high-field metal in a Kondo insulator
Ziji Xiang, Lu Chen, Kuan-Wen Chen +11
Within condensed-matter systems, strong electronic interactions often lead to exotic quantum phases. A recent manifestation of this is the unexpected observation of magnetic quantu…
Electron irradiation of Co, Ni, and P-doped BaFe2As2 - type iron-based superconductors
Cornelis Jacominus Van Der Beek, Sultan Demirdis, Dorothée Colson +7
High energy electron irradiation is used to controllably introduce atomic-scale point defects into single crystalline Ba(Fe_1-xCo_x)_2As_2, Ba(Fe_1-xNi_x)_2As_2, and BaFe_2(As_1-xP…
In Situ STM Observation of Nonmagnetic Impurity Effect in MBE-grown CeCoIn Films
Masahiro Haze, Yohei Torii, Robert Peters +5
Local electronic effects in the vicinity of an impurity provide pivotal insight into the origin of unconventional superconductivity, especially when the materials are located on th…
Low Energy Quasiparticle Excitation in the Vortex State of Borocarbide Superconductor YNi_2B_2C
K. Izawa, A. Shibata, Yuji Matsuda +5
We have measured the low temperature heat capacity Cp and microwave surface impedance Zs in the vortex state of YNi_2B_2C. In contrast to conventional s-wave superconductors, Cp sh…