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| 3. |
- Horio, M., et al.
(författare)
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Oxide Fermi liquid universality revealed by electron spectroscopy
- 2020
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 102:24
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Tidskriftsartikel (refereegranskat)abstract
- We present a combined soft x-ray and high-resolution vacuum-ultraviolet angle-resolved photoemission spectroscopy study of the electron-overdoped cuprate Pr1.3-xLa0.7CexCuO4 (PLCCO). Demonstration of its highly two-dimensional band structure enabled precise determination of the in-plane self-energy dominated by electron-electron scattering. Through analysis of this self-energy and the Fermi liquid cut-off energy scale, we find-in contrast to hole-doped cuprates-a momentum isotropic and comparatively weak electron correlation in PLCCO. Yet, the self-energies extracted from multiple oxide systems combine to demonstrate a logarithmic divergent relation between the quasiparticle scattering rate and mass. This constitutes a spectroscopic version of the Kadowaki-Woods relation with an important merit-the demonstration of Fermi liquid quasiparticle lifetime and mass being set by a single energy scale.
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| 6. |
- Sutter, D., et al.
(författare)
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Hallmarks of Hunds coupling in the Mott insulator Ca2RuO4
- 2017
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Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- A paradigmatic case of multi-band Mott physics including spin-orbit and Hund's coupling is realized in Ca2RuO4. Progress in understanding the nature of this Mott insulating phase has been impeded by the lack of knowledge about the low-energy electronic structure. Here we provide-using angle-resolved photoemission electron spectroscopy-the band structure of the paramagnetic insulating phase of Ca2RuO4 and show how it features several distinct energy scales. Comparison to a simple analysis of atomic multiplets provides a quantitative estimate of the Hund's coupling J = 0.4 eV. Furthermore, the experimental spectra are in good agreement with electronic structure calculations performed with Dynamical Mean-Field Theory. The crystal field stabilization of the d(xy) orbital due to c-axis contraction is shown to be essential to explain the insulating phase. These results underscore the importance of multi-band physics, Coulomb interaction and Hund's coupling that together generate the Mott insulating state of Ca2RuO4.
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| 7. |
- Horio, M., et al.
(författare)
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Electronic reconstruction forming a C-2-symmetric Dirac semimetal in Ca3Ru2O7
- 2021
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Ingår i: npj Quantum Materials. - : Springer Science and Business Media LLC. - 2397-4648. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Electronic band structures in solids stem from a periodic potential reflecting the structure of either the crystal lattice or electronic order. In the stoichiometric ruthenate Ca3Ru2O7, numerous Fermi surface-sensitive probes indicate a low-temperature electronic reconstruction. Yet, the causality and the reconstructed band structure remain unsolved. Here, we show by angle-resolved photoemission spectroscopy, how in Ca3Ru2O7 a C-2-symmetric massive Dirac semimetal is realized through a Brillouin-zone preserving electronic reconstruction. This Dirac semimetal emerges in a two-stage transition upon cooling. The Dirac point and band velocities are consistent with constraints set by quantum oscillation, thermodynamic, and transport experiments, suggesting that the complete Fermi surface is resolved. The reconstructed structure-incompatible with translational-symmetry-breaking density waves-serves as an important test for band structure calculations of correlated electron systems.
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| 8. |
- Horio, M., et al.
(författare)
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Orbital-selective metal skin induced by alkali-metal-dosing Mott-insulating Ca 2 RuO 4
- 2023
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Ingår i: Communications Physics. - 2399-3650. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Doped Mott insulators are the starting point for interesting physics such as high temperature superconductivity and quantum spin liquids. For multi-band Mott insulators, orbital selective ground states have been envisioned. However, orbital selective metals and Mott insulators have been difficult to realize experimentally. Here we demonstrate by photoemission spectroscopy how Ca2RuO4, upon alkali-metal surface doping, develops a single-band metal skin. Our dynamical mean field theory calculations reveal that homogeneous electron doping of Ca2RuO4 results in a multi-band metal. All together, our results provide evidence for an orbital-selective Mott insulator breakdown, which is unachievable via simple electron doping. Supported by a cluster model and cluster perturbation theory calculations, we demonstrate a type of skin metal-insulator transition induced by surface dopants that orbital-selectively hybridize with the bulk Mott state and in turn produce coherent in-gap states.
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| 9. |
- Marques, Carolina A., et al.
(författare)
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Spin-orbit coupling induced Van Hove singularity in proximity to a Lifshitz transition in Sr4Ru3O10
- 2024
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Ingår i: npj Quantum Materials. - 2397-4648. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Van Hove singularities (VHss) in the vicinity of the Fermi energy often play a dramatic role in the physics of strongly correlated electron materials. The divergence of the density of states generated by VHss can trigger the emergence of phases such as superconductivity, ferromagnetism, metamagnetism, and density wave orders. A detailed understanding of the electronic structure of these VHss is therefore essential for an accurate description of such instabilities. Here, we study the low-energy electronic structure of the trilayer strontium ruthenate Sr4Ru3O10, identifying a rich hierarchy of VHss using angle-resolved photoemission spectroscopy and millikelvin scanning tunneling microscopy. Comparison of k-resolved electron spectroscopy and quasiparticle interference allows us to determine the structure of the VHss and demonstrate the crucial role of spin-orbit coupling in shaping them. We use this to develop a minimal model from which we identify a mechanism for driving a field-induced Lifshitz transition in ferromagnetic metals.
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| 11. |
- Reid, A. H., et al.
(författare)
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Beyond a phenomenological description of magnetostriction
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Magnetostriction, the strain induced by a change in magnetization, is a universal effect in magnetic materials. Owing to the difficulty in unraveling its microscopic origin, it has been largely treated phenomenologically. Here, we show how the source of magnetostriction-the underlying magnetoelastic stress-can be separated in the time domain, opening the door for an atomistic understanding. X-ray and electron diffraction are used to separate the subpicosecond spin and lattice responses of FePt nanoparticles. Following excitation with a 50-fs laser pulse, time-resolved X-ray diffraction demonstrates that magnetic order is lost within the nanoparticles with a time constant of 146 fs. Ultrafast electron diffraction reveals that this demagnetization is followed by an anisotropic, three-dimensional lattice motion. Analysis of the size, speed, and symmetry of the lattice motion, together with ab initio calculations accounting for the stresses due to electrons and phonons, allow us to reveal the magnetoelastic stress generated by demagnetization.
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| 12. |
- Sutter, D., et al.
(författare)
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Orbitally selective breakdown of Fermi liquid quasiparticles in Ca1.8Sr0.2RuO4
- 2019
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 99:12
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Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive angle-resolved photoemission spectroscopy study of Ca1.8Sr0.2RuO4. Four distinct bands are revealed and along the Ru-O bond direction their orbital characters are identified through a light polarization analysis and comparison to dynamical mean-field theory calculations. Bands assigned to d(xz),d(yz) orbitals display Fermi liquid behavior with fourfold quasiparticle mass renormalization. Extremely heavy fermions-associated with a predominantly d(xy) band character-are shown to display non-Fermi-liquid behavior. We thus demonstrate that Ca1.8Sr0.2RuO4 is a hybrid metal with an orbitally selective Fermi liquid quasiparticle breakdown.
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| 13. |
- Ciancio, Regina, 1978, et al.
(författare)
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Atomic structure of functional interfaces in Sr2RuO4/Sr3Ru2O7 eutectic crystals
- 2009
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 95:14, s. 142507 (artno)-
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Tidskriftsartikel (refereegranskat)abstract
- Sr2RuO4/Sr3Ru2O7 eutectic system is investigated by transmission electron microscopy (TEM) and high angle annular dark field scanning TEM (STEM). The Sr2RuO4/Sr3Ru2O7 lamellar structure allows studying tunneling and proximity effects between spin-triplet superconductor Sr2RuO4 and metamagnetic normal metal Sr3Ru2O7. Our analyses reveal two typologies of interfaces within the eutectic: interfaces parallel to the growth direction are sharp and defect-free whereas interfaces perpendicular to the growth direction appear wavy and decorated with Ru precipitates. These results indicate that interfaces parallel to the growth direction are the best candidates for Sr2RuO4/Sr3Ru2O7 natural junctions to study the unusual superconductivity of Sr2RuO4. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3243691]
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| 14. |
- Ciancio, Regina, 1978, et al.
(författare)
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Electron backscattering diffraction and X-ray diffraction studies of interface relationships in Sr3Ru2O7/Sr2RuO4 eutectic crystals
- 2011
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Ingår i: Micron. - : Elsevier BV. - 0968-4328. ; 42:4, s. 324-329
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Tidskriftsartikel (refereegranskat)abstract
- Sr3Ru2O7/Sr2RuO4 eutectic system is investigated by electron backscattering diffraction (EBSD) and X-ray diffraction (XRD). The eutectic growth enables the solidification of the two phases in an ordered lamellar pattern extending along the growth direction, namely the b-axis direction. The eutectic material thus provides in the a-c plane two distinct interfaces having different microstructures with respect to the growth direction. Our analysis shows that, across the inplane c-axis direction (characterized by a poor lattice matching), the b-axis orientation is not constant at the individual interfaces, showing an orientation spread of about 5 degrees. However, across the in-plane a-axis direction (characterized by a good lattice matching), the b-axis orientation does not change within a few tenths of degree (about 0.25 degrees). Such information at nanoscale is also verified on a macroscopic level by standard XRD investigation.
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| 15. |
- Ciancio, Regina, 1978, et al.
(författare)
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Toward intrinsic functionalities of bilayered ruthenate Sr3Ru2O7
- 2009
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 80:5, s. 054110 (artno)-
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Tidskriftsartikel (refereegranskat)abstract
- Polymorphic materials are known for being prone to intergrowth. Remarkable examples are strontium ruthenates whose properties are dramatically tuned by impurities and disorder. In particular, Sr3Ru2O7 shows a strong variation in transport and magnetic properties depending on synthesis process. It is therefore crucial to correlate atomic structure and properties to identify the functionalities of individual nanostructural constituents. We report a comparative study between Sr3Ru2O7 crystals grown as single phase and in Sr3Ru2O7-Sr2RuO4 eutectics. Our analysis by transmission electron microscopy reveals that Sr3Ru2O7 domains of the eutectic have a significantly lower level of impurities compared to Sr3Ru2O7 single-phase crystals, where intergrowths of Sr4Ru3O10 and SrRuO3 phase are seen. This is confirmed by magnetic measurements. These results identify the eutectic solidification as a fruitful way to grow highly pure crystals of polymorphic materials which, in combination with recent technological developments allowing the extraction of embedded features of crystals, opens a pathway for understanding of their physical properties and applications.
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| 16. |
- Fittipaldi, R., et al.
(författare)
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Superconductivity in Sr2RuO4-Sr3Ru2O7 eutectic crystals
- 2008
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Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 83:2, s. Art. no. 27007-
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Tidskriftsartikel (refereegranskat)abstract
- Superconducting behavior has been observed in the Sr2RuO4-Sr3Ru2O7 eutectic system as grown by the flux-feeding floating-zone technique. A supercurrent flows across a single interface between Sr2RuO4 and Sr3Ru2O7 areas at distances that are far beyond those expected in a conventional proximity effect. The current-voltage characteristics within the Sr3Ru2O7 macrodomain, as extracted from the eutectic, exhibit signatures of superconductivity in the bilayered Sr3Ru2O7 region. Detailed microstructural, morphological and compositional analyses address issues on the concentration and the size of Sr2RuO4 inclusions within the Sr3Ru2O7 matrix. We speculate on the possibility of inhomogeneous superconductivity in the eutectic Sr3Ru2O7 and exotic pairing induced by the Sr2RuO4 inclusions. Copyright (C) EPLA, 2008.
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| 17. |
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| 18. |
- von Arx, K., et al.
(författare)
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Resonant inelastic x-ray scattering study of Ca3Ru2O7
- 2020
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 102:23
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Tidskriftsartikel (refereegranskat)abstract
- We present a combined oxygen K-edge x-ray absorption spectroscopy and resonant inelastic x-ray scattering (RIXS) study of the bilayer ruthenate Ca3Ru2O7. Our RIXS experiments on Ca3Ru2O7 were carried out on the overlapping planar and interplanar oxygen resonances, which are distinguishable from the apical one. Comparison to equivalent oxygen K-edge spectra recorded on band-Mott insulating Ca2RuO4 is made. In contrast to Ca2RuO4 spectra, which contain excitations linked to Mott physics, Ca3Ru2O7 spectra feature only intra-t(2g) ones that do not directly involve the Coulomb energy scale. As found in Ca2RuO4, we resolve two intra-t(2g) excitations in Ca3Ru2O7. Moreover, the lowest lying excitation in Ca3Ru2O7 shows a significant dispersion, revealing a collective character different from what is observed in Ca2RuO4. Theoretical modeling supports the interpretation of this lowest energy excitation in Ca3Ru2O7 as a magnetic transverse mode with multiparticle character, whereas the corresponding excitation in Ca2RuO4 is assigned to combined longitudinal and transverse spin modes. These fundamental differences are discussed in terms of the inequivalent magnetic ground-state manifestations in Ca2RuO4 and Ca3Ru2O7.
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