1,141 research outputs found
Properties of the Nearly Free Electron Superconductor Ag5Pb2O6 Inferred from Fermi Surface Measurements
We measured the Fermi surface of the recently discovered superconductor
Ag5Pb2O6 via a de Haas-van Alphen rotation study. Two frequency branches were
observed and identified with the neck and belly orbits of a very simple, nearly
free electron Fermi surface. We use the observed Fermi surface geometry to
quantitatively deduce superconducting properties such as the in-plane and
out-of-plane penetration depths, the coherence length in the clean limit, and
the critical field; as well as normal state properties such as the specific
heat and the resistivity anisotropy.Comment: 2 pages, 1 figure, submitted to Physica C (M2S Proceedings
Magnetism and superconductivity in TaSC (M = Fe, Co, Ni, and Cu)
Magnetic properties of TaSC ( = Fe, Co, Ni, Cu) have
been studied using SQUID DC and AC magnetic susceptibility. In these systems
magnetic ions are intercalated into van der Waals gaps between
adjacent S layers of host superconductor TaSC.
FeTaSC is a quasi 2D -like antiferromagnet on the
triangular lattice. It undergoes an antiferromagnetic phase transition at
(= 117 K). The irreversible effect of magnetization occurs below
, reflecting the frustrated nature of the system. The AF phase coexists
with two superconducting phases with the transition temperatures
K and K. CoTaSC is a quasi 2D Ising-like
antiferromagnet on the triangular lattice. The antiferromagnetic phase below
K coexists with a superconducting phase below K.
Both NiTaSC and CuTaSC are
superconductors with ( K for Ni and 6.4 K for Cu) and
(= 4.6 K common to TaSC). Very small effective magnetic
moments suggest that Ni and Cu spins are partially delocalized.Comment: 15 pages, 17 figures, and 3 table
Density Matrix Renormalization Group Study of the Disorder Line in the Quantum ANNNI Model
We apply Density Matrix Renormalization Group methods to study the phase
diagram of the quantum ANNNI model in the region of low frustration where the
ferromagnetic coupling is larger than the next-nearest-neighbor
antiferromagnetic one. By Finite Size Scaling on lattices with up to 80 sites
we locate precisely the transition line from the ferromagnetic phase to a
paramagnetic phase without spatial modulation. We then measure and analyze the
spin-spin correlation function in order to determine the disorder transition
line where a modulation appears. We give strong numerical support to the
conjecture that the Peschel-Emery one-dimensional line actually coincides with
the disorder line. We also show that the critical exponent governing the
vanishing of the modulation parameter at the disorder transition is .Comment: 4 pages, 5 eps figure
Fermiological Interpretation of Superconductivity/Non-superconductivity of FeTe_{1-x}Se_{x} Thin Crystal Determined by Quantum Oscillation Measurement
We have successfully observed quantum oscillation (QO) for FeTe_{1-x}Se_{x}.
QO measurements were performed using non-superconducting and superconducting
thin crystals of FeTe_{0.65}Se_{0.35} fabricated by the scotch-tape method. We
show that the Fermi surfaces (FS) of the non-superconducting crystal are in
good agreement with the rigid band shift model based on electron doping by
excess Fe while that of the superconducting crystal is in good agreement with
the calculated FS with no shift. From the FS comparison of both crystals, we
demonstrate the change of the cross-sectional area of the FS, suggesting that
the suppression of the FS nesting with the vector Q_{s} = (\pi, \pi) due to
excess Fe results in the disappearance of the superconductivity.Comment: 8 pages, 4 figure
Direct Observation of Nonequivalent Fermi-Arc States of Opposite Surfaces in Noncentrosymmetric Weyl Semimetal NbP
We have performed high-resolution angle-resolved photoemission spectroscopy
(ARPES) on noncentrosymmetric Weyl semimetal candidate NbP, and determined the
electronic states of both Nb- and P-terminated surfaces corresponding to the
"opposite" surfaces of a polar crystal. We revealed a drastic difference in the
Fermi-surface topology between the opposite surfaces, whereas the Fermi arcs on
both surfaces are likely terminated at the surface projection of the same bulk
Weyl nodes. Comparison of the ARPES data with our first-principles band
calculations suggests notable difference in electronic structure at the
Nb-terminated surface between theory and experiment. The present result opens a
platform for realizing exotic quantum phenomena arising from unusual surface
properties of Weyl semimetals.Comment: 5 pages, 4 figure
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