277 research outputs found
Rigid-Band Shift of the Fermi Level in a Strongly Correlated Metal: Sr(2-y)La(y)RuO(4)
We report a systematic study of electron doping of Sr2RuO4 by non-isovalent
substitution of La^(3+) for Sr^(2+). Using a combination of de Haas-van Alphen
oscillations, specific heat, and resistivity measurements, we show that
electron doping leads to a rigid-band shift of the Fermi level corresponding to
one doped electron per La ion, with constant many-body quasiparticle mass
enhancement over the band mass. The susceptibility spectrum is substantially
altered and enhanced by the doping but this has surprisingly little effect on
the strength of the unconventional superconducting pairing.Comment: 4 pages, 3 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
Spin-Orbit-Induced Orbital Excitations in Sr2RuO4 and Ca2RuO4: A Resonant Inelastic X-ray Scattering Study
High-resolution resonant inelastic X-ray scattering (RIXS) at the oxygen
K-edge has been used to study the orbital excitations of Ca2RuO4 and Sr2RuO4.
In combination with linear dichroism X-ray absorption spectroscopy, the
ruthenium 4d-orbital occupation and excitations were probed through their
hybridization with the oxygen p-orbitals. These results are described within a
minimal model, taking into account crystal field splitting and a spin-orbit
coupling \lambda_{so}=200~meV. The effects of spin-orbit interaction on the
electronic structure and implications for the Mott and superconducting ground
states of (Ca,Sr)2RuO4 are discussed.Comment: accepted in PRB 201
The Lorenz ratio as a guide to scattering contributions to Planckian transport
In many physical situations in which many-body assemblies exist at
temperature , a characteristic quantum-mechanical time scale of
approximately can be identified in both theory and experiment,
leading to speculation that it may be the shortest meaningful time in such
circumstances. When this behaviour is investigated by probing the scattering
rate of strongly interacting electrons in metals, it is clear that in some
cases only electron-electron scattering can be its cause, while in others it
arises from high-temperature scattering of electrons from quantised lattice
vibrations, i.e. phonons. In metallic oxides, which are among the most studied
materials, analysis of electrical transport does not satisfactorily identify
the relevant scattering mechanism at 'high' temperatures near room temperature.
We employ a contactless optical method to measure thermal diffusivity in two
Ru-based layered perovskites, SrRuO and SrRuO, and use the
measurements to extract the dimensionless Lorenz ratio. By comparing our
results to the literature data on both conventional and unconventional metals
we show how the analysis of high-temperature thermal transport can both give
important insight into dominant scattering mechanisms, and be offered as a
stringent test of theories attempting to explain anomalous scattering.Comment: 27 pages, 8 figure
Effects of In-Plane Impurity Substitution in Sr2RuO4
We report comparative substitution effects of nonmagnetic Ti^(4+) and
magnetic Ir^(4+) impurities for Ru^(4+) in the spin-triplet superconductor
Sr2RuO4. We found that both impurities suppress the superconductivity
completely at a concentration of approximately 0.15%, reflecting the high
sensitivity to translational symmetry breaking in Sr2RuO4. In addition, a rapid
enhancement of residual resistivity is in quantitative agreement with
unitarity-limit scattering. Our result suggests that both nonmagnetic and
magnetic impurities in Sr2RuO4 act as strong potential scatterers, similar to
the nonmagnetic Zn^(2+) impurity in the high-Tc cuprates.Comment: 4 pages, 2 figures. submitted to Journal of the Physical Society of
Japa
Dynamical properties of charged stripes in La(2-x)SrxCuO4
Inelastic light-scattering spectra of underdoped La_2−xSr_xCuO4 single crystals are presented which provide direct evidence of the formation of quasi-one-dimensional charged structures in the two-dimensional CuO2 planes. The stripes manifest themselves in a Drude-like peak at low energies and temperatures. The selection rules allow us to determine the orientation to be along the diagonals at x=0.02 and along the principal axes at x=0.10. The electron-lattice interaction determines the correlation length which turns out to be larger in compound classes with lower superconducting transition temperatures. Temperature is the only scale of the response at different doping levels demonstrating the importance of quantum critical behavior
Phenomenology of the normal state in-plane transport properties of high- cuprates
In this article, I review progress towards an understanding of the normal
state (in-plane) transport properties of high- cuprates in the light of
recent developments in both spectroscopic and transport measurement techniques.
Against a backdrop of mounting evidence for anisotropic single-particle
lifetimes in cuprate superconductors, new results have emerged that advocate
similar momentum dependence in the transport decay rate ({\bf k}). In
addition, enhancement of the energy scale (up to the bare bandwidth) over which
spectroscopic information on the quasiparticle response can be obtained has led
to the discovery of new, unforeseen features that surprisingly, may have a
significant bearing on the transport properties at the dc limit. With these two
key developments in mind, I consider here whether all the ingredients necessary
for a complete phenomenological description of the anomalous normal state
transport properties of high- cuprates are now in place.Comment: 31 pages, 10 figure
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