A5023713151- Physics of Superconductivity and Magnetism
- Iron-based superconductors research
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Magnetic properties of thin films
- Rare-earth and actinide compounds
- Topological Materials and Phenomena
- High-pressure geophysics and materials
- Quantum and electron transport phenomena
- Organic and Molecular Conductors Research
- Superconductivity in MgB2 and Alloys
- Superconducting Materials and Applications
- Graphene research and applications
- 2D Materials and Applications
- Magnetic Properties and Applications
- Theoretical and Computational Physics
- Electronic and Structural Properties of Oxides
- Chalcogenide Semiconductor Thin Films
- Chemical and Physical Properties of Materials
- Magnetic Properties of Alloys
- Geomagnetism and Paleomagnetism Studies
- Acoustic Wave Resonator Technologies
- Surface and Thin Film Phenomena
- Characterization and Applications of Magnetic Nanoparticles
- Quantum many-body systems
RIKEN Center for Emergent Matter Science
2016-2025
RIKEN
2004-2021
ORCID
2021
RIKEN Advanced Science Institute
2009-2014
Japan Science and Technology Agency
1999-2012
Kyoto University
2002-2009
Rutgers, The State University of New Jersey
2009
Kyoto University Institute for Chemical Research
2007-2009
Japan Atomic Energy Agency
2009
Advanced Science Research Center
2009
Removing electrons from the CuO2 plane of cuprates alters electronic correlations sufficiently to produce high-temperature superconductivity. Associated with these changes are spectral weight transfers high energy states insulator low energies. In theory, should be detectable as an imbalance between tunneling rate for electron injection and extraction - a asymmetry. We introduce atomic-resolution tunneling-asymmetry imaging, finding virtually identical phenomena in two lightly hole-doped...
Mazin and Singh comment that the peaks in Fourier-transformed spectroscopic maps of Fe(Se,Te) are not related to quasi-particle-interference (QPI) but may be Bragg associated with chalcogen lattice possible surface reconstruction which would triggered by surface-induced spin-density wave. We show too broad assigned as consistent QPI.
Significance The BCS-BEC (Bardeen–Cooper–Schrieffer––Bose–Einstein-condensate) cross-over bridges the two important theories of bound particles in a unified picture with ratio attractive interaction to Fermi energy as tuning parameter. A key issue is understand intermediate regime, where new states matter may emerge. Here, we show that FeSe extremely small, resulting this system can be regarded an extraordinary “high-temperature” superconductor located at verge cross-over. Most importantly,...
We investigate Dirac fermions on the surface of topological insulator Bi2Se3 using scanning tunneling spectroscopy. Landau levels (LLs) are observed in spectra a magnetic field. In contrast to LLs conventional electrons, field independent LL appears at point, which is hallmark fermions. A scaling analysis based Bohr-Sommerfeld quantization condition allowed us determine dispersion band. Near Fermi energy, fine peaks mixed with appear spectra, may be responsible for anomalous...
Abstract If a material with an odd number of electrons per unit-cell is insulating, Mott localisation may be invoked as explanation. This widely accepted for the layered compound 1 T -TaS 2 , which has low-temperature insulating phase comprising charge order clusters 13 unpaired orbitals each. But if stacking layers doubles to include even orbitals, nature state ambiguous. Here, scanning tunnelling microscopy reveals two distinct terminations in sign such double-layer pattern. However,...
We investigate vortices in LiFeAs using scanning tunneling microscopy/spectroscopy. Zero-field spectra show two superconducting gaps without detectable spectral weight near the Fermi energy, evidencing fully-gapped multi-band superconductivity. image a wide field range from 0.1 T to 11 by mapping conductance at energy. A quasi-hexagonal vortex lattice low contains domain boundaries which consist of alternating with unusual coordination numbers 5 and 7. With increasing field, become...
High-temperature superconductivity and a wide variety of exotic superconducting states discovered in FeSe-based materials have been at the frontier research on condensed matter physics over past decade. Unique properties originating from multiband electronic structure, strongly orbital-dependent phenomena, extremely small Fermi energy, nematicity, topological aspects give rise to many distinct fascinating states. Here, we provide an overview our current understanding {\it bulk} materials,...
Magnetic skyrmions were thought to be stabilised only in inversion-symmetry breaking structures, but skyrmion lattices recently discovered inversion symmetric Gd-based compounds, spurring questions of the stabilisation mechanism. A natural consequence a recent theoretical proposal, coupling between itinerant electrons and localised magnetic moments, is that are amenable detection using even non-magnetic probes such as spectroscopic-imaging scanning tunnelling microscopy (SI-STM). Here SI-STM...
Scanning tunneling microscopy reveals the relationship between nematicity and superconductivity in an iron-based superconductor.
Junctions and interfaces consisting of unconventional superconductors provide an excellent experimental playground to study exotic phenomena related the phase order parameter. Not only complex structure parameters have impact on Josephson effects, but also may profoundly alter quasi-particle excitation spectrum near a junction. Here, by using spectroscopic-imaging scanning tunneling microscopy, we visualize spatial evolution local density states (LDOS) twin boundaries (TBs) nodal...
When electrons pair in a superconductor, quasi-particles develop an acute sensitivity to different types of scattering potential that is described by the appearance coherence factors amplitudes. Although effects are well established isotropic superconductors, they much harder detect their anisotropic counterparts, such as high-superconducting-transition-temperature cuprates. We demonstrate approach highlights momentum-dependent Ca 2– x Na CuO 2 Cl . used Fourier-transform scanning tunneling...
Ultrasound velocity measurements of the unconventional superconductor ${\mathrm{CeCoIn}}_{5}$ with extremely large Pauli paramagnetic susceptibility reveal an unusual structural transformation flux-line lattice (FLL) in vicinity upper critical field. The transition field coincides that at which heat capacity a second-order phase transition. lowering sound is consistent vortex segmentation and crossover to quasi-two-dimensional FLL pinning. These results provide strong evidence high-field...
FeSe is argued as a superconductor in the Bardeen-Cooper-Schrieffer Bose-Einstein-condensation crossover regime where superconducting-gap size and superconducting transition temperature Tc are comparable to Fermi energy. In this regime, vortex bound states should be well quantized preformed pairs above may yield pseudogap quasiparticle-excitation spectrum. We performed spectroscopic-imaging scanning tunneling microscopy search for these features. found Friedel-like oscillations near vortex,...
Conventional superconductivity follows Bardeen-Cooper-Schrieffer(BCS) theory of electrons-pairing in momentum-space, while superfluidity is the Bose-Einstein condensation(BEC) atoms paired real-space. These properties solid metals and ultra-cold gases, respectively, are connected by BCS-BEC crossover. Here we investigate band dispersions FeTe(0.6)Se(0.4)(Tc = 14.5 K ~ 1.2 meV) an accessible range below above Fermi level(EF) using ultra-high resolution laser angle-resolved photoemission...
Abstract A bulk superconductor possessing a topological surface state at the Fermi level is promising system to realise long-sought superconductivity. Although several candidate materials have been proposed, experimental demonstrations concurrently exploring spin textures and superconductivity remained elusive. Here we perform spectroscopic-imaging scanning tunnelling microscopy on centrosymmetric β -PdBi 2 that hosts state. By combining first-principles electronic-structure calculations...
The spatial variation of electronic states was imaged in the lightly doped Mott insulator Ca_{2-x}Na_{x}CuO_{2}Cl_{2} using scanning tunneling microscopy / spectroscopy (STM/STS). We observed nano-scale domains with a high local density within an insulating background. have characteristic length scale 2 nm (~4-5a, a:lattice constant) preferred orientations along tetragonal [100] direction. argue that such spatially inhomogeneous are inherent to slightly insulators and play important role for...
A vortex in an s-wave superconductor with a surface Dirac cone can trap Majorana bound state zero energy leading to zero-bias peak (ZBP) of tunneling conductance. The iron-based FeTe$_x$Se$_{1-x}$ is one the material candidates hosting these modes. It has been observed by recent scanning spectroscopy measurement that fraction cores possessing ZBPs decreases increasing magnetic field on this superconductor. We construct three-dimensional tight-binding model simulating physics over hundred...
Superconductors can be used as dissipation-free electrical conductors long vortices are pinned. Vortices in high-temperature superconductors, however, behave anomalously, reflecting the anisotropic layered structure, and move readily, thus preventing their practical use. Specifically, a magnetic field tilted toward layer plane, special vortex arrangement (chain-lattice state) is formed. Real-time observation of using high-resolution Lorentz microscopy revealed that images chain begin to...