77 research outputs found
A self-consistent method for X-ray diffraction analysis of multiaxial residual-stress fields in the near-surface region of polycrystalline materials. II. Examples
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
Decoupling carrier concentration and electron-phonon coupling in oxide heterostructures observed with resonant inelastic x-ray scattering
We report the observation of multiple phonon satellite features in ultra thin
superlattices of form SrIrO/SrTiO using resonant inelastic x-ray
scattering. As the values of and vary the energy loss spectra show a
systematic evolution in the relative intensity of the phonon satellites. Using
a closed-form solution for the cross section, we extract the variation in the
electron-phonon coupling strength as a function of and . Combined with
the negligible carrier doping into the SrTiO layers, these results indicate
that tuning of the electron-phonon coupling can be effectively decoupled from
doping. This work showcases both a feasible method to extract the
electron-phonon coupling in superlattices and unveils a potential route for
tuning this coupling which is often associated with superconductivity in
SrTiO-based systems.Comment: 4 pages, 5 figure
Ion pairing versus water structure modifications
The effect of monovalent cations (Li+, K+, NH4 +, Na +) on the water structure
in aqueous chloride and acetate solutions was characterized by oxygen K-edge
X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy, and resonant
inelastic X-ray scattering (RIXS) of a liquid microjet. We show ion- and
counterion dependent effects on the emission spectra of the oxygen K-edge,
which we attribute to modifications of the hydrogen bond network of water. For
acetates, ion pairing with carboxylates was also probed selectively by XAS and
RIXS. We correlate our experimental results to speciation data and to the
salting-out properties of the cations
Charge ordering in Ir dimers in the ground state of BaAlIrO
It has been well established experimentally that the interplay of electronic
correlations and spin-orbit interactions in Ir and Ir oxides
results in insulating J=1/2 and J=0 ground states,
respectively. However, in compounds where the structural dimerization of iridum
ions is favourable, the direct Ir -- hybridisation can be significant and
takes a key role. Here, we investigate the effects of direct Ir --
hybridisation in comparison with electronic correlations and spin-orbit
coupling in BaAlIrO, a compound with Ir dimers. Using a
combination of many-body wave function quantum chemistry
calculations and resonant inelastic X-ray scattering (RIXS) experiments, we
elucidate the electronic structure of BaAlIrO. We find excellent
agreement between the calculated and the measured spin-orbit excitations.
Contrary to the expectations, the analysis of the many-body wave function shows
that the two Ir (Ir and Ir) ions in the IrO dimer unit in
this compound preserve their local J character close to 1/2 and 0,
respectively. The local point group symmetry at each of the Ir sites assumes an
important role, significantly limiting the direct -- hybridisation. Our
results emphasize that minute details in the local crystal field (CF)
environment can lead to dramatic differences in electronic states in iridates
and 5 oxides in general.Comment: 5 pages with 3 figure
Damped spin excitations in a doped cuprate superconductor with orbital hybridization
A resonant inelastic x-ray scattering study of overdamped spin excitations in slightly underdoped La2−x Srx CuO4 (LSCO) with x = 0.12 and 0.145 is presented. Three high-symmetry directions have been investigated: (1) the antinodal (0,0) → ( 1 ,0), (2) the nodal (0,0) → ( 1 , 1 ), and (3) the zone-boundary direction
2 4 4 ( 1 1 1 2 ,0) → ( 4 ,4 ) connecting these two. The overdamped excitations exhibit strong dispersions along (1) and (3), whereas a much more modest dispersion is found along (2). This is in strong contrast to the undoped compound
La2CuO4 (LCO) for which the strongest dispersions are found along (1) and (2). The t − t i − t ii − U Hubbard model used to explain the excitation spectrum of LCO predicts—for constant U/t —that the dispersion along (3) scales with (t i/t )2. However, the diagonal hopping t i extracted on LSCO using single-band models is low (t i/t ∼ −0.16) and decreasing with doping. We therefore invoked a two-orbital (dx2 −y2 and dz2 ) model which implies that t i is enhanced. This effect acts to enhance the zone-boundary dispersion within the Hubbard model. We thus conclude that hybridization of dx2 −y2 and dz2 states has a significant impact on the zone-boundary dispersion in LSCO
Coupled Cu and Mn charge and orbital orders in YBa₂Cu₃O₇/Nd 0.65 (Ca 1-y Sr y ) 0.35 MnO₃ multilayers
The observation of a charge density wave in the underdoped cuprate high Tc superconductors (Cu-CDW) raised a debate about its relationship with superconductivity. In bulk YBa2Cu3O7−δ the Cu-CDW is incipient and mainly pinned by defects. Nevertheless, a large magnetic field can induce a true long-range Cu- CDW order as it suppresses superconductivity. An enhanced Cu-CDW order was also observed in YBa2Cu3O7/La2/3Ca1/3MnO3 multilayers. Here, we show that the magnitude of the Cu-CDW in YBa2Cu3O7−δ / Nd0.65(Ca1-ySry)0.35MnO3 multilayers can be varied by adjusting the strength of the manganite charge and orbital order via the Sr content (tolerance factor). Furthermore, we resolve the reconstruction of the crystal field levels of the interfacial Cu ions that are also affected by the manganite charge and orbital order. This tuneable interfacial coupling and Cu- CDW in YBa2Cu3O7−δ can be used for studying the relationship between the Cu- CDW and superconductivity and, possibly, for inducing new intertwined quantum states
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