1,427 research outputs found
Possible pairing symmetries in SrPtAs with a local lack of inversion center
We discuss possible pairing symmetries in the hexagonal pnictide
superconductor SrPtAs. The local lack of inversion symmetry of the two distinct
conducting layers in the unit cell results in a special spin-orbit coupling
with a staggered structure. We classify the pairing symmetry by the global
crystal point group D_3d, and suggest some candidates for the stable state
using a tight-binding model with an in-plane, density-density type pairing
interaction. We may have some unconventional states like s+f-wave and a mixture
of chiral d-wave and chiral p-wave. The spin orbit coupling is larger than the
interlayer hopping, and the mixing between spin-singlet and triplet states can
be seen in spite of the fact that the system has a global inversion center.Comment: 5 pages, 3 figure
Dimensional crossover in SrRuO within slave-boson mean-field theory
Motivated by the anomalous temperature dependence of the c-axis resistivity
of SrRuO, the dimensional crossover from a network of perpendicular
one-dimensional chains to a two-dimensional system due to a weak hybridization
between the perpendicular chains is studied. The corresponding two-orbital
Hubbard model is treated within a slave-boson mean-field theory (SBMFT) to take
correlation effects into account such as the spin-charge separation on the
one-dimensional chains. Using an RPA-like formulation for the Green's function
of collective spinon-holon excitations the emergence of quasiparticles at
low-temperatures is examined. The results are used to discuss the evolution of
the spectral density and the c-axis transport within a tunneling approach. For
the latter a regime change between low- and high-temperature regime is found in
qualitative accordance with experimental data
Phase transition in the 3 Kelvin phase in the eutectic Sr2RuO4-Ru
The inhomogeneous 3-Kelvin (3K) phase of the eutectic Sr2RuO4 with Ru
inclusions nucleates superconductivity at the interface between Ru and Sr2RuO4.
The structure of the interface state and its physical properties are examined
here. Two superconducting phases are identified between the transitions to the
bulk phase at 1.5K and to the 3K phase. The nucleation of the 3K phase results
in a state conserving time reversal symmetry, which generates an intrinsically
frustrated superconducting network in samples with many Ru inclusions. At a
lower temperature (>1.5K), a discontinuous (first order) transition to an
interface state breaking time reversal symmetry is found leading to an
unfrustrated network phase. It is shown that this phase transition located at a
temperature between 1.5 and 3K would yield the anomalous property that the
critical current in such a network depends on the sign of the current,
reproducing recent experimental observations.Comment: This paper has been withdrawn by the authors. 5 pages, 6 figure
Magnetic response of nonmagnetic impurities in cuprates
A theory of the local magnetic response of a nonmagnetic impurity in a doped
antiferromagnet, as relevant to the normal state in cuprates, is presented. It
is based on the assumption of the overdamped collective mode in the bulk system
and on the evidence, that equal-time spin correlations are only weakly
renormalized in the vicinity of the impurity. The theory relates the Kondo-like
behavior of the local susceptibility to the anomalous temperature dependence of
the bulk magnetic susceptibility, where the observed increase of the Kondo
temperature with doping reflects the crossover to the Fermi liquid regime and
the spatial distribution of the magnetization is given by bulk
antiferromagnetic correlations.Comment: 5 pages, 3 figure
Mid-infrared laser spectroscopic determination of isotope ratios of N2O at trace levels using wavelength modulation and balanced path length detection
We present a new mid-infrared laser spectrometer for high-precision measurements of isotopic ratios of molecules at ppm concentrations. Results are discussed for nitrous oxide (N2O), where a precision of 3‰ for a single measurement and a reproducibility of 6‰ have been achieved for a concentration of 825ppm. The room-temperature laser source employed is based on difference-frequency generation delivering a continuous-wave power up to 23μW at wavelengths between 4.3μm and 4.7μm and a line width of 1MHz. Two different measurement methods are compared; wavelength modulation with first-harmonic detection and direct absorption spectroscopy by recording the spectrum with a data-acquisition card. Two different detection schemes were employed; either all isotopomers were measured using the long path (36m) of the multipass cell or a balanced path length detection scheme was used, where the main isotope was measured with a beam along a shorter path (40cm) in the multipass cell. A single-pass reference cell was designed, offering two different path lengths for balanced path length detection. All combinations of measurement methods and detection schemes were tested regarding precision of a single measurement and long-term stability. The advantages and disadvantages of various measurement approaches are discusse
Superconductivity without Local Inversion Symmetry; Multi-layer Systems
While multi-layer systems can possess global inversion centers, they can have
regions with locally broken inversion symmetry. This can modify the
superconducting properties of such a system. Here we analyze two dimensional
multi-layer systems yielding spatially modulated antisymmetric spin-orbit
coupling (ASOC) and discuss superconductivity with mixed parity order
parameters. In particular, the influence of ASOC on the spin susceptibility is
investigated at zero temperature. For weak inter-layer coupling we find an
enhanced spin susceptibility induced by ASOC, which hints the potential
importance of this aspect for superconducting phase in specially structured
superlattices.Comment: 4 pages, 2 figures, proceedings of the 26th International Conference
on Low Temperature Physics (LT26
Magnetic domain formation in itinerant metamagnets
We examine the effects of long-range dipolar forces on metamagnetic
transitions and generalize the theory of Condon domains to the case of an
itinerant electron system undergoing a first-order metamagnetic transition. We
demonstrate that within a finite range of the applied field, dipolar
interactions induce a spatial modulation of the magnetization in the form of
stripes or bubbles. Our findings are consistent with recent observations in the
bilayer ruthenate SrRuO.Comment: 4 pages, 3 figures, minor changes, references adde
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