46 research outputs found
Interplay between multiple charge-density waves and the relationship with superconductivity in PdHoTe
HoTe, a member of the rare-earth tritelluride (Te) family, and
its Pd-intercalated compounds, PdHoTe, where superconductivity (SC)
sets in as the charge-density wave (CDW) transition is suppressed by the
intercalation of a small amount of Pd, are investigated using angle-resolved
photoemission spectroscopy (ARPES) and electrical resistivity. Two
incommensurate CDWs with perpendicular nesting vectors are observed in
HoTe at low temperatures. With a slight Pd intercalation ( = 0.01),
the large CDW gap decreases and the small one increases. The momentum
dependence of the gaps along the inner Fermi surface (FS) evolves from
orthorhombicity to near tetragonality, manifesting the competition between two
CDW orders. At = 0.02, both CDW gaps decreases with the emergence of SC.
Further increasing the content of Pd for = 0.04 will completely suppress
the CDW instabilities and give rise to the maximal SC order. The evolution of
the electronic structures and electron-phonon couplings (EPCs) of the multiple
CDWs upon Pd intercalation are carefully scrutinized. We discuss the interplay
between multiple CDW orders, and the competition between CDW and SC in detail.Comment: 6 pages, 5 figure
Observation of oscillatory relaxation in the Sn-terminated surface of epitaxial rock-salt SnSe topological crystalline insulator
Topological crystalline insulators have been recently predicted and observed
in rock-salt structure SnSe thin films. Previous studies have
suggested that the Se-terminated surface of this thin film with hydrogen
passivation, has a reduced surface energy and is thus a preferred
configuration. In this paper, synchrotron-based angle-resolved photoemission
spectroscopy, along with density functional theory calculations, are used to
demonstrate conclusively that a rock-salt SnSe thin film
epitaxially-grown on \ce{Bi2Se3} has a stable Sn-terminated surface. These
observations are supported by low energy electron diffraction (LEED)
intensity-voltage measurements and dynamical LEED calculations, which further
show that the Sn-terminated SnSe thin film has undergone a surface
structural relaxation of the interlayer spacing between the Sn and Se atomic
planes. In sharp contrast to the Se-terminated counterpart, the observed Dirac
surface state in the Sn-terminated SnSe thin film is shown to yield a
high Fermi velocity, m/s, which suggests a potential mechanism
of engineering the Dirac surface state of topological materials by tuning the
surface configuration.Comment: 12 pages, 13 figures, supplementary materials include
Time correlation of success recanalization for endovascular recanalization of medically refractory non-acute intracranial arterial occlusions
Background and purposeThe management of patients with symptomatic non-acute atherosclerotic intracranial artery occlusion (sNAA-ICAO), which is a special subset with high morbidity and a high probability of recurrent serious ischemic events despite standard medical therapy, has been clinically challenging. A number of small-sample clinical studies have discussed endovascular recanalization for sNAA-ICAO and the lack of a uniform standard of operation time. The purpose of this study was to investigate the time correlation of successful recanalization.MethodsFrom January 2013 to August 2021, 69 consecutive patients who underwent endovascular recanalization for sNAA-ICAO were analyzed retrospectively in the First Affiliated Hospital of Harbin Medical University. The technical success rate, periprocedural complications, and rate of TIA/ischemic stroke during follow-up were evaluated.ResultsThe overall technical success rate was 73.91% (51/69), and the rate of perioperative complications was 37.68% (26/69). The percentage of patients with perioperative symptoms was 27.53% (19/69). The rate of serious symptomatic perioperative complications was 8.70% (6/69). After adjusting for age, sex, and BMI, the effect of the time from the last symptom to operation on successful recanalization was 0.42 (IQR, 0.20, 0.88, P = 0.021), before the inflection point (51 days).ConclusionsEndovascular recanalization for sNAA-ICAO is technically feasible in reasonably selected patients. The perioperative safety is within the acceptable range. Before 51 days, the last symptoms to operation time, for every 10 days of delay, the probability of successful recanalization is reduced by 57%
Inhomogeneous d-wave superconducting state of a doped Mott insulator
Recent scanning tunneling microscope (STM) measurements discovered remarkable
electronic inhomogeneity, i.e. nano-scale spatial variations of the local
density of states (LDOS) and the superconducting energy gap, in the high-Tc
superconductor BSCCO. Based on the experimental findings we conjectured that
the inhomogeneity arises from variations in local oxygen doping level and may
be generic of doped Mott insulators which behave rather unconventionally in
screening the dopant ionic potentials at atomic scales comparable to the short
coherence length. Here, we provide theoretical support for this picture. We
study a doped Mott insulator within a generalized t-J model, where doping is
accompanied by ionic Coulomb potentials centered in the BiO plane. We calculate
the LDOS spectrum, the integrated LDOS, and the local superconducting gap, make
detailed comparisons to experiments, and find remarkable agreement with the
experimental data. We emphasize the unconventional screening in a doped Mott
insulator and show that nonlinear screening dominates at nano-meter scales
which is the origin of the electronic inhomogeneity. It leads to strong
inhomogeneous redistribution of the local hole density and promotes the notion
of a local doping concentration. We find that the inhomogeneity structure
manifests itself at all energy scales in the STM tunneling differential
conductance, and elucidate the similarity and the differences between the data
obtained in the constant tunneling current mode and the same data normalized to
reflect constant tip-to-sample distance. We also discuss the underdoped case
where nonlinear screening of the ionic potential turns the spatial electronic
structure into a percolative mixture of patches with smaller pairing gaps
embedded in a background with larger gaps to single particle excitations.Comment: 19 pages, final versio