1,034 research outputs found
Ultrafast nematic-orbital excitation in FeSe
The electronic nematic phase is an unconventional state of matter that
spontaneously breaks the rotational symmetry of electrons. In
iron-pnictides/chalcogenides and cuprates, the nematic ordering and
fluctuations have been suggested to have as-yet-unconfirmed roles in
superconductivity. However, most studies have been conducted in thermal
equilibrium, where the dynamical property and excitation can be masked by the
coupling with the lattice. Here we use femtosecond optical pulse to perturb the
electronic nematic order in FeSe. Through time-, energy-, momentum- and
orbital-resolved photo-emission spectroscopy, we detect the ultrafast dynamics
of electronic nematicity. In the strong-excitation regime, through the
observation of Fermi surface anisotropy, we find a quick disappearance of the
nematicity followed by a heavily-damped oscillation. This short-life nematicity
oscillation is seemingly related to the imbalance of Fe 3dxz and dyz orbitals.
These phenomena show critical behavior as a function of pump fluence. Our
real-time observations reveal the nature of the electronic nematic excitation
instantly decoupled from the underlying lattice
Glucose-sulfate conjugates as a new phase II metabolite formed by aquatic crustaceans
ArticleBIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS. 360(2): 490-495 (2007)journal articl
Momentum dependence of the energy gap in the superconducting state of optimally doped Bi2(Sr,R)2CuOy (R=La and Eu)
The energy gap of optimally doped Bi2(Sr,R)2CuOy (R=La and Eu) was probed by
angle resolved photoemission spectroscopy (ARPES) using a vacuum ultraviolet
laser (photon energy 6.994 eV) or He I resonance line (21.218 eV) as photon
source. The results show that the gap around the node at sufficiently low
temperatures can be well described by a monotonic d-wave gap function for both
samples and the gap of the R=La sample is larger reflecting the higher Tc.
However, an abrupt deviation from the d-wave gap function and an opposite R
dependence for the gap size were observed around the antinode, which represent
a clear disentanglement between the antinodal pseudogap and the nodal
superconducting gap.Comment: Submitted as the proceedings of LT2
Observation of Jonscher Law in AC Hopping Conduction of Electron-Doped Nanoporous Crystal 12CaO7Al2O3 in THz Frequency Range
We have performed terahertz time-domain spectroscopy of carrier-doped
nanoporous crystal 12CaO7Al2O3 showing the Mott variable range hopping at room
temperature. The real part of the dielectric constant clearly demonstrates the
nature of localized carriers. The frequency dependence of both the real and
imaginary parts of the dielectric constant can be simply explained by assuming
two contributions: a dielectric response by the parent compound with no
carriers and an AC hopping conduction with the Jonscher law generally reported
up to GHz range. The possible obedience to the Jonscher law in the THz range
suggests a relaxation time of the hopping carriers much faster than 1ps in the
carrier-doped 12CaO7Al2O3.Comment: 4pages 3figures. to be published in Phys. Rev.
Pseudogap of metallic layered nickelate R2-xSrxNiO4 (R=Nd, Eu) crystals measured using angle-resolved photoemission spectroscopy
We have investigated charge dynamics and electronic structures for single
crystals of metallic layered nickelates, R2-xSrxNiO4 (R=Nd, Eu), isostructural
to La2-xSrxCuO4. Angle-resolved photoemission spectroscopy on the
barely-metallic Eu0.9Sr1.1NiO4 (R=Eu, x=1.1) has revealed a large hole surface
of x2-y2 character with a high-energy pseudogap of the same symmetry and
comparable magnitude with those of underdoped (x<0.1) cuprates, although the
antiferromagnetic interactions are one order of magnitude smaller. This finding
strongly indicates that the momentum-dependent pseudogap feature in the layered
nickelate arises from the real-space charge correlation.Comment: 4 pages, 4 figures. Accepted in Physical Review Letter
Three-dimensional bulk band dispersion in polar BiTeI with giant Rashba-type spin splitting
In layered polar semiconductor BiTeI, giant Rashba-type spin-split band
dispersions show up due to the crystal structure asymmetry and the strong
spin-orbit interaction. Here we investigate the 3-dimensional (3D) bulk band
structures of BiTeI using the bulk-sensitive -dependent soft x-ray angle
resolved photoemission spectroscopy (SX-ARPES). The obtained band structure is
shown to be well reproducible by the first-principles calculations, with huge
spin splittings of meV at the conduction-band-minimum and
valence-band-maximum located in the plane. It provides the first
direct experimental evidence of the 3D Rashba-type spin splitting in a bulk
compound.Comment: 9 pages, 4 figure
Strongly spin-orbit coupled two-dimensional electron gas emerging near the surface of polar semiconductors
We investigate the two-dimensional (2D) highly spin-polarized electron
accumulation layers commonly appearing near the surface of n-type polar
semiconductors BiTeX (X = I, Br, and Cl) by angular-resolved photoemission
spectroscopy. Due to the polarity and the strong spin-orbit interaction built
in the bulk atomic configurations, the quantized conduction-band subbands show
giant Rashba-type spin-splitting. The characteristic 2D confinement effect is
clearly observed also in the valence-bands down to the binding energy of 4 eV.
The X-dependent Rashba spin-orbit coupling is directly estimated from the
observed spin-split subbands, which roughly scales with the inverse of the
band-gap size in BiTeX.Comment: 15 pages 4 figure
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