336 research outputs found
Absence of orbital-selective Mott transition in Ca_2-xSr_xRuO4
Quasi-particle spectra of the layer perovskite SrRuO are calculated
within Dynamical Mean Field Theory for increasing values of the on-site Coulomb
energy . At small the planar geometry splits the bands near
into a wide, two-dimensional band and two narrow, nearly
one-dimensional bands. At larger , however, the spectral
distribution of these states exhibit similar correlation features, suggesting a
common metal-insulator transition for all bands at the same critical
.Comment: 4 pages, 4 figure
Spectroscopy of SrRuO/Ru Junctions in Eutectic
We have investigated the tunnelling properties of the interface between
superconducting Sr2RuO4 and a single Ru inclusion in eutectic. By using a
micro-fabrication technique, we have made Sr2RuO4/Ru junctions on the eutectic
system that consists of Sr2RuO4 and Ru micro-inclusions. Such a eutectic system
exhibits surface superconductivity, called the 3-K phase. A zero bias
conductance peak (ZBCP) was observed in the 3-K phase. We propose to use the
onset of the ZBCP to delineate the phase boundary of a time-reversal symmetry
breaking state.Comment: To be published in Proc of 24th Int. Conf. on Low Temperature Physics
(LT24); 2 page
Orbital-dependent metamagnetic response in Sr4Ru3O10
We show that the metamagnetic transition in SrRuO bifurcates
into two transitions as the field is rotated away from the conducting planes.
This two-step process comprises partial or total alignment of moments in
ferromagnetic bands followed by an itinerant metamagnetic transition whose
critical field increases with rotation. Evidence for itinerant metamagnetism is
provided by the Shubnikov-de Hass effect which shows a non-trivial evolution of
the geometry of the Fermi surface and an enhancement of the quasiparticles
effective-mass across the transition. The metamagnetic response of
SrRuO is orbital-dependent and involves ferromagnetic and
metamagnetic bands.Comment: Physical Review B (in press
Anisotropy of the incommensurate fluctuations in Sr2RuO4: a study with polarized neutrons
The anisotropy of the magnetic incommensurate fluctuations in Sr2RuO4 has
been studied by inelastic neutron scattering with polarized neutrons. We find a
sizeable enhancement of the out of plane component by a factor of two for
intermediate energy transfer which appears to decrease for higher energies. Our
results qualitatively confirm calculations of the spin-orbit coupling, but the
experimental anisotropy and its energy dependence are weaker than predicted.Comment: 4 pages, 4 figure
The de Haas-van Alphen effect across the metamagnetic transition in SrRuO
We report a study of the de Haas-van Alphen (dHvA) effect on the itinerant
metamagnet SrRuO. Extremely high sample purity allows the
observation of dHvA oscillations both above and below the metamagnetic
transition field of 7.9 T. The quasiparticle masses are fairly large away from
the transition, and are enhanced by up to an extra factor of three as the
transition is approached, but the Fermi surface topography change is quite
small. The results are qualitatively consistent with a field-induced Stoner
transition in which the mass enhancement is the result of critical
fluctuations.Comment: 4 pages, 3 figure
Anisotropy in the Antiferromagnetic Spin Fluctuations of Sr2RuO4
It has been proposed that Sr_2RuO_4 exhibits spin triplet superconductivity
mediated by ferromagnetic fluctuations. So far neutron scattering experiments
have failed to detect any clear evidence of ferromagnetic spin fluctuations
but, instead, this type of experiments has been successful in confirming the
existence of incommensurate spin fluctuations near q=(1/3 1/3 0). For this
reason there have been many efforts to associate the contributions of such
incommensurate fluctuations to the mechanism of its superconductivity. Our
unpolarized inelastic neutron scattering measurements revealed that these
incommensurate spin fluctuations possess c-axis anisotropy with an anisotropic
factor \chi''_{c}/\chi''_{a,b} of \sim 2.8. This result is consistent with some
theoretical ideas that the incommensurate spin fluctuations with a c-axis
anisotropy can be a origin of p-wave superconductivity of this material.Comment: 5 pages, 3 figures; accepted for publication in PR
Isotope effect in superconductors with coexisting interactions of phonon and nonphonon mechanisms
We examine the isotope effect of superconductivity in systems with coexisting
interactions of phonon and nonphonon mechanisms in addition to the direct
Coulomb interaction. The interaction mediated by the spin fluctuations is
discussed as an example of the nonphonon interaction. Extended formulas for the
transition temperature Tc and the isotope-effect coefficient alpha are derived
for cases (a) omega_np omega_D, where omega_np is
an effective cutoff frequency of the nonphonon interaction that corresponds to
the Debye frequency omega_D in the phonon interaction. In case (a), it is found
that the nonphonon interaction does not change the condition for the inverse
isotope effect, i.e., mu^* > lambda_ph/2, but it modifies the magnitude of
alpha markedly. In particular, it is found that a giant isotope shift occurs
when the phonon and nonphonon interactions cancel each other largely. For
instance, strong critical spin fluctuations may give rise to the giant isotope
effect. In case (b), it is found that the inverse isotope effect occurs only
when the nonphonon interaction and the repulsive Coulomb interaction, in total
effect, work as repulsive interactions against the superconductivity. We
discuss the relevance of the present result to some organic superconductors,
such as kappa-(ET)2Cu(NCS)2 and Sr2RuO4 superconductors, in which inverse
isotope effects have been observed, and briefly to high-Tc cuprates, in which
giant isotope effects have been observed.Comment: 4 pages, 2 figures, (with jpsj2.cls, ver.1.2), v2:linguistic
correction
Two-dimensional incommensurate magnetic fluctuations in Sr(RuTi)O
We investigate the imaginary part of the wave vector dependent dynamic spin
susceptibility in Sr(RuTi)O as a function of
temperature using neutron scattering. At T=5 K, two-dimensional incommensurate
(IC) magnetic fluctuations are clearly observed around
up to approximately 60 meV energy transfer.
We find that the IC excitations disperse to ridges around the
point. Below 50 K, the energy and temperature dependent excitations are well
described by the phenomenological response function for a Fermi liquid system
with a characteristic energy of 4.0(1) meV. Although the wave vector dependence
of the IC magnetic fluctuations in Sr(RuTi)O is
similar to that in the Fermi liquid state of the parent compound,
SrRuO, the magnetic fluctuations are clearly suppressed by the
Ti-doping.Comment: 5 pages, 4 figure
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