716 research outputs found
Enhanced thermoelectric properties by Ir doping of PtSb2 with pyrite structure
The effects of Ir doping on the thermoelectric properties of Pt1-xIrxSb2 (x =
0, 0.01, 0.03, and 0.1) with pyrite structure were studied. Measurements of
electrical resistivity rho, Seebeck coefficient S, and thermal conductivity
kappa were conducted. The results showed an abrupt change from semiconducting
behavior without Ir (x = 0) to metallic behavior at x = 0.01. The sample with x
= 0.01 exhibited large S and low rho, resulting in a maximum power factor
(S^2/rho) of 43 muW/cmK^2 at 400 K. The peculiar "pudding mold"-type electronic
band dispersion could explain the enhanced thermoelectric properties in the
metallic state.Comment: 3 pages, 2 figure
Directional tunnelling spectroscopy of a normal metal--wave superconductor junction
We calculate the normal metal--wave superconductor tunnelling spectrum
for various junction orientations and for two forms of the superconducting gap,
one which allows for point nodes and the other which allows for line nodes. For
a junction oriented with its normal parallel to the ab plane of the tetragonal
superconductor, we find that the tunnelling spectrum is strongly dependent on
orientation in the plane. The spectrum contains two peaks at energies
equivalent to the magnitudes of the gap function in the direction parallel to
the interface normal and in the direction making a angle with the
normal. These two peaks appear in both superconductors with point nodes and
line nodes, but are more prominent in the latter. For the tunnelling along the
c axis, we find a sharp peak at the gap maximum in the conductance spectrum of
the superconductor with line nodes, whereas with point nodes we find a peak
occurring at the value of the gap function along the c axis. We discuss the
relevance of our result to borocarbide systems.Comment: 16 pages, 10 figure
Josephson effect in a weak link between borocarbides
A stationary Josephson effect is analyzed theoretically for a weak link
between borocarbide superconductors. It is shown that different models of the
order parameter result in qualitatively different current-phase relations
Fulde-Ferrell-Larkin-Ovchinnikov state in a perpendicular field of quasi two-dimensional CeCoIn5
A Fulde-Ferrell-Larkin-Ovchinnkov (FFLO) state was previously reported in the
quasi-2D heavy fermion CeCoIn5 when a magnetic field was applied parallel to
the ab-plane. Here, we conduct 115^In NMR studies of this material in a
PERPENDICULAR field, and provide strong evidence for FFLO in this case as well.
Although the topology of the phase transition lines in the H-T phase diagram is
identical for both configurations, there are several remarkable differences
between them. Compared to H//ab, the FFLO region for H perpendicular to the
ab-plane shows a sizable decrease, and the critical field separating the FFLO
and non-FFLO superconducting states almost ceases to have a temperature
dependence. Moreover, directing H perpendicular to the ab-plane results in a
notable change in the quasiparticle excitation spectrum within the planar node
associated with the FFLO transition.Comment: 5 pages, 3 figure
Orbital Degeneracy and Peierls Instability in Triangular Lattice Superconductor IrPtTe
We have studied electronic structure of triangular lattice
IrPtTe superconductor using photoemission spectroscopy and
model calculations. Ir core-level photoemission spectra show that Ir
charge modulation established in the low temperature phase of IrTe
is suppressed by Pt doping. This observation indicates that the suppression of
charge modulation is related to the emergence of superconductivity.
Valence-band photoemission spectra of IrTe suggest that the Ir charge
modulation is accompanied by Ir orbital reconstruction. Based on the
photoemission results and model calculations, we argue that the
orbitally-induced Peierls effect governs the charge and orbital instability in
the IrPtTe.Comment: 5 pages,4 figure
- …