1,188 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
Soil water retention curve of agrogray soils: influence of anisotropy and the scaling factor
The soil water characteristic or soil water retention curve (WRC) of medium-loamy gray forest soil horizons was studied in cylinder-shaped samples of disturbed and undisturbed structure. The sample height varied within 2-4 cm and the diameter within 4.5-10 cm. The soil monoliths were sampled in three profiles: vertically, along the slope, and across the slope in accordance with the intrasoil paleorelief formed by the fun-nel-shaped surface of the second humus horizon. The experimental WRC were approximated with the van Genuchten equatio
Electronic band structure, Fermi surface, and elastic properties of new 4.2K superconductor SrPtAs from first-principles calculations
The hexagonal phase SrPtAs (s.g. P6/mmm; #194) with a honeycomb lattice
structure very recently was declared as a new low-temperature (TC ~ 4.2K)
superconductor. Here by means of first-principles calculations the optimized
structural parameters, electronic bands, Fermi surface, total and partial
densities of states, inter-atomic bonding picture, independent elastic
constants, bulk and shear moduli for SrPtAs were obtained for the first time
and analyzed in comparison with the related layered superconductor SrPt2As2.Comment: 8 pages, 4 figure
Electronic Structures of CaAlSi with Different Stacking AlSi Layers by First-Principles Calculations
The full-potential linear augmented plane-wave calculations have been applied
to investigate the systematic change of electronic structures in CaAlSi due to
different stacking sequences of AlSi layers. The present ab-initio calculations
have revealed that the multistacking, buckling and 60 degrees rotation of AlSi
layer affect the electronic band structure in this system. In particular, such
a structural perturbation gives rise to the disconnected and cylindrical Fermi
surface along the M-L lines of the hexagonal Brillouin zone. This means that
multistacked CaAlSi with the buckling AlSi layers increases degree of
two-dimensional electronic characters, and it gives us qualitative
understanding for the quite different upper critical field anisotropy between
specimens with and without superstructure as reported previously.Comment: 4 pages, 4 figures, to be published in J. Phys. Soc. Jp
Correlated band structure of superconducting NdFeAsO0.9F0.1: Dynamical mean-field study
We report the LDA + DMFT (method combining local density approximation with dynamical mean-field theory) results for spectral properties of the superconductor NdFeAsO0.9F0.1 in the paramagnetic phase. The calculated momentum-resolved spectral functions are in good agreement with angle-resolved photoemission spectra (ARPES). The obtained effective quasiparticle mass enhancement (m*/m = 1.4) is smaller than the one in isostructural parent compound LaFeAsO which critical temperature under the same fluorine doping (LaFeAsO0.9F0.1) is two times lower. Our results demonstrate that in quaternary FeAs-based superconductors of the same class, changes of the crystal structure caused by substitution of one rare-earth atom, implicitly result in reduction of the electronic correlation strength. © 2013 Pleiades Publishing, Inc
Structural, elastic and electronic properties of new layered superconductor HfCuGe2 in comparison with isostructural HfCuSi2, ZrCuGe2, and ZrCuSi2 from first-principles calculations
Very recently, low-temperature superconductivity was discovered for the intermetallic compound HfCuGe2 (2013; Cava RJ, et al, EPL 101:67001.), which was declared as "a non-magnetic analog of the 1111 iron pnictides". Herein, by means of the first-principles calculations, we have examined in detail the structural, elastic, and electronic properties of HfCuGe2, as well as of the isostructural and isoelectronic phases ZrCuGe2, HfCuSi2, and ZrCuSi2, which are analyzed in comparison with a set of 1111-like phases. The obtained close similarity of the electronic factors, namely, the topologies of the near-Fermi bands, the Fermi surfaces, as well as the DOS values at the Fermi level for superconducting HfCuGe2 and other examined 112 phases allowed us to assume that low-temperature superconductivity may be expected also for ZrCuGe2, HfCuSi2, and ZrCuSi2. © 2013 Elsevier Ltd. All rights reserved
Anatomy of the band structure of the newest apparent near-ambient superconductor LuHN
Recently it was claimed that nitrogen-doped lutetium hydride exhibited a
near-ambient superconducting transition with a temperature of 294 K at a
pressure of only 10 kbar, this pressure being several orders of magnitude lower
than previously demonstrated for hydrides under pressure. In this paper, we
investigate within DFT+U the electronic structure of both parent lutetium
hydride LuH and nitrogen doped lutetium hydride LuHN. We
calculated corresponding bands, density of states and Fermi surfaces. It is
shown that in the stoichiometric system the Lu-5d states cross the Fermi level
while the H-1s states make almost no contribution at the Fermi level. However,
with nitrogen doping, the N-2p states enter the Fermi level in large quantities
and bring together a significant contribution from the H-1s states. The
presence of N-2p and H-1s states at the Fermi level in a doped compound can
facilitate the emergence of superconductivity. For instance, nitrogen doping
almost doubles the value of DOS at the Fermi level. Simple BCS analysis shows
that the nitrogen doping of LuH can provide T more than 100K and even
increase it with further hole doping.Comment: 7 pages, 5 figure
Full Relativistic Electronic Structure and Fermi Surface Sheets of the First Honeycomb-Lattice Pnictide Superconductor SrPtAs
We report full-potential density functional theory (DFT)-based {\it ab
initio} band structure calculations to investigate electronic structure
properties of the first pnictide superconductor with a honeycomb-lattice
structure: SrPtAs. As a result, electronic bands, density of states, Fermi
velocities and the topology of the Fermi surface for SrPtAs are obtained. These
quantities are discussed in comparison to the first available experimental
data. Predictions for future measurements are provided
Contrasting Pressure Effects in Sr2VFeAsO3 and Sr2ScFePO3
We report the resistivity measurements under pressure of two Fe-based
superconductors with a thick perovskite oxide layer, Sr2VFeAsO3 and Sr2ScFePO3.
The superconducting transition temperature Tc of Sr2VFeAsO3 markedly increases
with increasing pressure. Its onset value, which was Tc{onset}=36.4 K at
ambient pressure, increases to Tc{onset}=46.0 K at ~4 GPa, ensuring the
potential of the "21113" system as a high-Tc material. However, the
superconductivity of Sr2ScFePO3 is strongly suppressed under pressure. The
Tc{onset} of ~16 K decreases to ~5 K at ~4 GPa, and the zero-resistance state
is almost lost. We discuss the factor that induces this contrasting pressure
effect.Comment: 5 pages, 4 figures, to be published in J. Phys. Soc. Jpn. No.12
(2009
- …