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Bouravleuv AD, Lev LL, Piamonteze C, Wang X, Schmitt T, Khrebtov AI, Samsonenko YB, Kanski J, Cirlin GE, Strocov VN. Electronic structure of (In,Mn)As quantum dots buried in GaAs investigated by soft-x-ray ARPES. NANOTECHNOLOGY 2016; 27:425706. [PMID: 27631689 DOI: 10.1088/0957-4484/27/42/425706] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Electronic structure of a molecular beam epitaxy-grown system of (In,Mn)As quantum dots (QDs) buried in GaAs is explored with soft-x-ray angle-resolved photoelectron spectroscopy (ARPES) using photon energies around 1 keV. This technique, ideally suited for buried systems, extends the momentum-resolving capabilities of conventional ARPES with enhanced probing depth as well as elemental and chemical state specificity achieved with resonant photoexcitation. The experimental results resolve the dispersive energy bands of the GaAs substrate buried in ∼2 nm below the surface, and the impurity states (ISs) derived from the substitutional Mn atoms in the (In,Mn)As QDs and oxidized Mn atoms distributed near the surface. An energy shift of the Mn ISs in the QDs compared to (In,Mn)As DMS is attributed to the band offset and proximity effect at the interface with the surrounding GaAs. The absence of any ISs in the vicinity of the VBM relates the electron transport in (In,Mn)As QDs to the prototype (In,Mn)As diluted magnetic semiconductor. The SX-ARPES results are supported by measurements of the shallow core levels under variation of probing depth through photon energy. X-ray absorption measurements identify significant diffusion of interstitial Mn atoms out of the QDs towards the surface, and the role of magnetic circular dichroism is to block the ferromagnetic response of the (In,Mn)As QDs. Possible routes are drawn to tune the growth procedure aiming at practical applications of the (In,Mn)As based systems.
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Bisogni V, Catalano S, Green RJ, Gibert M, Scherwitzl R, Huang Y, Strocov VN, Zubko P, Balandeh S, Triscone JM, Sawatzky G, Schmitt T. Ground-state oxygen holes and the metal-insulator transition in the negative charge-transfer rare-earth nickelates. Nat Commun 2016; 7:13017. [PMID: 27725665 PMCID: PMC5062575 DOI: 10.1038/ncomms13017] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2016] [Accepted: 08/25/2016] [Indexed: 11/13/2022] Open
Abstract
The metal–insulator transition and the intriguing physical properties of rare-earth perovskite nickelates have attracted considerable attention in recent years. Nonetheless, a complete understanding of these materials remains elusive. Here we combine X-ray absorption and resonant inelastic X-ray scattering (RIXS) spectroscopies to resolve important aspects of the complex electronic structure of rare-earth nickelates, taking NdNiO3 thin film as representative example. The unusual coexistence of bound and continuum excitations observed in the RIXS spectra provides strong evidence for abundant oxygen holes in the ground state of these materials. Using cluster calculations and Anderson impurity model interpretation, we show that distinct spectral signatures arise from a Ni 3d8 configuration along with holes in the oxygen 2p valence band, confirming suggestions that these materials do not obey a conventional positive charge-transfer picture, but instead exhibit a negative charge-transfer energy in line with recent models interpreting the metal–insulator transition in terms of bond disproportionation. Rare-earth perovskite nickelates show intriguing metal–insulator transitions, whose mechanism remains elusive. Here, Bisogni et al. evidenced a 3d8 Ni configuration together with abundance of oxygen 2p holes in the ground state of a NdNiO3 thin film, suggesting a negative charge-transfer scenario.
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Fabbris G, Meyers D, Okamoto J, Pelliciari J, Disa AS, Huang Y, Chen ZY, Wu WB, Chen CT, Ismail-Beigi S, Ahn CH, Walker FJ, Huang DJ, Schmitt T, Dean MPM. Orbital Engineering in Nickelate Heterostructures Driven by Anisotropic Oxygen Hybridization rather than Orbital Energy Levels. PHYSICAL REVIEW LETTERS 2016; 117:147401. [PMID: 27740843 DOI: 10.1103/physrevlett.117.147401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Indexed: 06/06/2023]
Abstract
Resonant inelastic x-ray scattering is used to investigate the electronic origin of orbital polarization in nickelate heterostructures taking LaTiO_{3}-LaNiO_{3}-3×(LaAlO_{3}), a system with exceptionally large polarization, as a model system. We find that heterostructuring generates only minor changes in the Ni 3d orbital energy levels, contradicting the often-invoked picture in which changes in orbital energy levels generate orbital polarization. Instead, O K-edge x-ray absorption spectroscopy demonstrates that orbital polarization is caused by an anisotropic reconstruction of the oxygen ligand hole states. This provides an explanation for the limited success of theoretical predictions based on tuning orbital energy levels and implies that future theories should focus on anisotropic hybridization as the most effective means to drive large changes in electronic structure and realize novel emergent phenomena.
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Dantz M, Pelliciari J, Samal D, Bisogni V, Huang Y, Olalde-Velasco P, Strocov VN, Koster G, Schmitt T. Quenched Magnon excitations by oxygen sublattice reconstruction in (SrCuO2)n/(SrTiO3)2 superlattices. Sci Rep 2016; 6:32896. [PMID: 27616448 PMCID: PMC5018731 DOI: 10.1038/srep32896] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 08/16/2016] [Indexed: 11/14/2022] Open
Abstract
The recently discovered structural reconstruction in the cuprate superlattice (SrCuO2)n/(SrTiO3)2 has been investigated across the critical value of n = 5 using resonant inelastic x-ray scattering (RIXS). We find that at the critical value of n, the cuprate layer remains largely in the bulk-like two-dimensional structure with a minority of Cu plaquettes being reconstructed. The partial reconstruction leads to quenching of the magnons starting at the Γ-point due to the minority plaquettes acting as scattering points. Although comparable in relative abundance, the doped charge impurities in electron-doped cuprate superconductors do not show this quenching of magnetic excitations.
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Reguesse AS, Szwebel JD, Schmitt T, Levan P. [When love becomes eternal: Two embedded rings, a case report]. ANN CHIR PLAST ESTH 2016; 62:109-112. [PMID: 27156132 DOI: 10.1016/j.anplas.2016.03.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 03/24/2016] [Indexed: 10/21/2022]
Abstract
Embedded ring injury is a rare condition often associated with mental illness or cognitive disorders. Clinical presentation varies from simple oedema to serious neurovascular deficits. We report the unusual case of a 69-year-old woman presenting with two embedded ring injuries. The rings had been in place for over 20 years, however she had no past medical history of psychiatric or neurological disorder. A non-invasive approach was decided to treat the patient by simply cutting the rings allowing to resolve the situation without further morbidity.
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Johnston S, Monney C, Bisogni V, Zhou KJ, Kraus R, Behr G, Strocov VN, Málek J, Drechsler SL, Geck J, Schmitt T, van den Brink J. Electron-lattice interactions strongly renormalize the charge-transfer energy in the spin-chain cuprate Li2CuO2. Nat Commun 2016; 7:10563. [PMID: 26884151 PMCID: PMC4757783 DOI: 10.1038/ncomms10563] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 12/26/2015] [Indexed: 11/09/2022] Open
Abstract
Strongly correlated insulators are broadly divided into two classes: Mott-Hubbard insulators, where the insulating gap is driven by the Coulomb repulsion U on the transition-metal cation, and charge-transfer insulators, where the gap is driven by the charge-transfer energy Δ between the cation and the ligand anions. The relative magnitudes of U and Δ determine which class a material belongs to, and subsequently the nature of its low-energy excitations. These energy scales are typically understood through the local chemistry of the active ions. Here we show that the situation is more complex in the low-dimensional charge-transfer insulator Li2CuO2, where Δ has a large non-electronic component. Combining resonant inelastic X-ray scattering with detailed modelling, we determine how the elementary lattice, charge, spin and orbital excitations are entangled in this material. This results in a large lattice-driven renormalization of Δ, which significantly reshapes the fundamental electronic properties of Li2CuO2.
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Schreck S, Pietzsch A, Kennedy B, Såthe C, Miedema PS, Techert S, Strocov VN, Schmitt T, Hennies F, Rubensson JE, Föhlisch A. Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering. Sci Rep 2016; 7:20054. [PMID: 26821751 PMCID: PMC4731820 DOI: 10.1038/srep20054] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 11/27/2015] [Indexed: 11/24/2022] Open
Abstract
Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future.
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Cancellieri C, Mishchenko AS, Aschauer U, Filippetti A, Faber C, Barišić OS, Rogalev VA, Schmitt T, Nagaosa N, Strocov VN. Polaronic metal state at the LaAlO3/SrTiO3 interface. Nat Commun 2016; 7:10386. [PMID: 26813124 PMCID: PMC4737810 DOI: 10.1038/ncomms10386] [Citation(s) in RCA: 112] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 12/03/2015] [Indexed: 11/16/2022] Open
Abstract
Interplay of spin, charge, orbital and lattice degrees of freedom in oxide heterostructures results in a plethora of fascinating properties, which can be exploited in new generations of electronic devices with enhanced functionalities. The paradigm example is the interface between the two band insulators LaAlO3 and SrTiO3 that hosts a two-dimensional electron system. Apart from the mobile charge carriers, this system exhibits a range of intriguing properties such as field effect, superconductivity and ferromagnetism, whose fundamental origins are still debated. Here we use soft-X-ray angle-resolved photoelectron spectroscopy to penetrate through the LaAlO3 overlayer and access charge carriers at the buried interface. The experimental spectral function directly identifies the interface charge carriers as large polarons, emerging from coupling of charge and lattice degrees of freedom, and involving two phonons of different energy and thermal activity. This phenomenon fundamentally limits the carrier mobility and explains its puzzling drop at high temperatures.
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Rogalev VA, Gröning O, Widmer R, Dil JH, Bisti F, Lev LL, Schmitt T, Strocov VN. Fermi states and anisotropy of Brillouin zone scattering in the decagonal Al-Ni-Co quasicrystal. Nat Commun 2015; 6:8607. [PMID: 26443439 PMCID: PMC4633949 DOI: 10.1038/ncomms9607] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 09/10/2015] [Indexed: 11/08/2022] Open
Abstract
Quasicrystals (QCs) are intermetallic alloys that have excellent long-range order but lack translational symmetry in at least one dimension. The valence band electronic structure near the Fermi energy EF in such materials is of special interest since it has a direct relation to their unusual physical properties. However, the Fermi surface (FS) topology as well as the mechanism of QC structure stabilization are still under debate. Here we report the first observation of the three-dimensional FS and valence band dispersions near EF in decagonal Al70Ni20Co10 (d-AlNiCo) QCs using soft X-ray angle-resolved photoemission spectroscopy. We show that the FS, formed by dispersive Al sp-states, has a multicomponent character due to a large contribution from high-order bands. Moreover, we discover that the magnitude of the gap at the FS related to the interaction with Brillouin zone boundary (Hume-Rothery gap) critically differs for the periodic and quasiperiodic directions.
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60
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Schmitt T, Mayer-Steinacker R, Mayer F, Grünwald V, schütte J, Hartmann J, Kasper B, Hüsing J, Hajda J, Ottawa G, Heilig C, Ho A, Egerer G. 3431 Vorinostat in locally advanced and metastastic soft tissue sarcomas - results of a multi-center phase II trial (SAHA-1) of the German Sarcoma and GIST Working Group (AIO). Eur J Cancer 2015. [DOI: 10.1016/s0959-8049(16)31904-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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61
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Meissner J, Tichy D, Katzke V, Kühn T, Dietrich S, Schmitt T, Ziepert M, Kuhnt E, Rixecker T, Zorn M, Witzens-Harig M, Pfreundschuh M, Ho A. Long-term ovarian function in women treated with CHOP or CHOP plus etoposide for aggressive lymphoma. Ann Oncol 2015; 26:1771-6. [DOI: 10.1093/annonc/mdv227] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 05/04/2015] [Indexed: 01/01/2023] Open
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62
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Hahn M, Böttcher S, Dietrich S, Hegenbart U, Rieger M, Stadtherr P, Bondong A, Schulz R, Ritgen M, Schmitt T, Tran TH, Görner M, Herth I, Luft T, Schönland S, Witzens-Harig M, Zenz T, Kneba M, Ho AD, Dreger P. Allogeneic hematopoietic stem cell transplantation for poor-risk CLL: dissecting immune-modulating strategies for disease eradication and treatment of relapse. Bone Marrow Transplant 2015; 50:1279-85. [DOI: 10.1038/bmt.2015.150] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 05/21/2015] [Accepted: 05/22/2015] [Indexed: 12/21/2022]
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63
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Minola M, Dellea G, Gretarsson H, Peng YY, Lu Y, Porras J, Loew T, Yakhou F, Brookes NB, Huang YB, Pelliciari J, Schmitt T, Ghiringhelli G, Keimer B, Braicovich L, Le Tacon M. Collective nature of spin excitations in superconducting cuprates probed by resonant inelastic X-ray scattering. PHYSICAL REVIEW LETTERS 2015; 114:217003. [PMID: 26066453 DOI: 10.1103/physrevlett.114.217003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Indexed: 06/04/2023]
Abstract
We used resonant inelastic x-ray scattering (RIXS) with and without analysis of the scattered photon polarization, to study dispersive spin excitations in the high temperature superconductor YBa_{2}Cu_{3}O_{6+x} over a wide range of doping levels (0.1≤x≤1). The excitation profiles were carefully monitored as the incident photon energy was detuned from the resonant condition, and the spin excitation energy was found to be independent of detuning for all x. These findings demonstrate that the largest fraction of the spin-flip RIXS profiles in doped cuprates arises from magnetic collective modes, rather than from incoherent particle-hole excitations as recently suggested theoretically [Benjamin et al. Phys. Rev. Lett. 112, 247002 (2014)]. Implications for the theoretical description of the electron system in the cuprates are discussed.
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Rubensson JE, Söderström J, Binggeli C, Gråsjö J, Andersson J, Såthe C, Hennies F, Bisogni V, Huang Y, Olalde P, Schmitt T, Strocov VN, Föhlisch A, Kennedy B, Pietzsch A. Rydberg-resolved resonant inelastic soft x-ray scattering: dynamics at core ionization thresholds. PHYSICAL REVIEW LETTERS 2015; 114:133001. [PMID: 25884123 DOI: 10.1103/physrevlett.114.133001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Indexed: 06/04/2023]
Abstract
Resonant inelastic x-ray scattering spectra excited in the immediate vicinity of the core-level ionization thresholds of N2 have been recorded. Final states of well-resolved symmetry-selected Rydberg series converging to valence-level ionization thresholds with vibrational excitations are observed. The results are well described by a quasi-two-step model which assumes that the excited electron is unaffected by the radiative decay. This threshold dynamics simplifies the interpretation of resonant inelastic x-ray scattering spectra considerably and facilitates characterization of low-energy excited final states in molecular systems.
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Bisogni V, Wohlfeld K, Nishimoto S, Monney C, Trinckauf J, Zhou K, Kraus R, Koepernik K, Sekar C, Strocov V, Büchner B, Schmitt T, van den Brink J, Geck J. Orbital control of effective dimensionality: from spin-orbital fractionalization to confinement in the anisotropic ladder system CaCu(2)O(3). PHYSICAL REVIEW LETTERS 2015; 114:096402. [PMID: 25793832 DOI: 10.1103/physrevlett.114.096402] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Indexed: 06/04/2023]
Abstract
Fractionalization of an electronic quasiparticle into spin, charge, and orbital parts is a fundamental and characteristic property of interacting electrons in one dimension. However, real materials are never strictly one dimensional and the fractionalization phenomena are hard to observe. Here we studied the spin and orbital excitations of the anisotropic ladder material CaCu_{2}O_{3}, whose electronic structure is not one dimensional. Combining high-resolution resonant inelastic x-ray scattering experiments with theoretical model calculations, we show that (i) spin-orbital fractionalization occurs in CaCu_{2}O_{3} along the leg direction x through the xz orbital channel as in a 1D system, and (ii) no fractionalization is observed for the xy orbital, which extends in both leg and rung direction, contrary to a 1D system. We conclude that the directional character of the orbital hopping can select different degrees of dimensionality. Using additional model calculations, we show that spin-orbital separation is generally far more robust than the spin-charge separation. This is not only due to the already mentioned selection realized by the orbital hopping, but also due to the fact that spinons are faster than the orbitons.
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Pietzsch A, Hennies F, Miedema PS, Kennedy B, Schlappa J, Schmitt T, Strocov VN, Föhlisch A. Snapshots of the fluctuating hydrogen bond network in liquid water on the sub-femtosecond timescale with vibrational resonant inelastic x-ray scattering. PHYSICAL REVIEW LETTERS 2015; 114:088302. [PMID: 25768783 DOI: 10.1103/physrevlett.114.088302] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Indexed: 05/24/2023]
Abstract
Liquid water molecules interact strongly with each other, forming a fluctuating hydrogen bond network and thereby giving rise to the anomalous phase diagram of liquid water. Consequently, symmetric and asymmetric water molecules have been found in the picosecond time average with IR and optical Raman spectroscopy. With subnatural linewidth resonant inelastic x-ray scattering (RIXS) at vibrational resolution, we take sub-femtosecond snapshots of the electronic and structural properties of water molecules in the hydrogen bond network. We derive a strong dominance of nonsymmetric molecules in liquid water in contrast to the gas phase on the sub-femtosecond timescale of RIXS and determine the fraction of highly asymmetrically distorted molecules.
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Tabis W, Li Y, Le Tacon M, Braicovich L, Kreyssig A, Minola M, Dellea G, Weschke E, Veit MJ, Ramazanoglu M, Goldman AI, Schmitt T, Ghiringhelli G, Barišić N, Chan MK, Dorow CJ, Yu G, Zhao X, Keimer B, Greven M. Charge order and its connection with Fermi-liquid charge transport in a pristine high-T(c) cuprate. Nat Commun 2014; 5:5875. [PMID: 25522689 DOI: 10.1038/ncomms6875] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 11/17/2014] [Indexed: 11/09/2022] Open
Abstract
Electronic inhomogeneity appears to be an inherent characteristic of the enigmatic cuprate superconductors. Here we report the observation of charge-density-wave correlations in the model cuprate superconductor HgBa2CuO(4+δ) (T(c)=72 K) via bulk Cu L3-edge-resonant X-ray scattering. At the measured hole-doping level, both the short-range charge modulations and Fermi-liquid transport appear below the same temperature of about 200 K. Our result points to a unifying picture in which these two phenomena are preceded at the higher pseudogap temperature by q=0 magnetic order and the build-up of significant dynamic antiferromagnetic correlations. The magnitude of the charge modulation wave vector is consistent with the size of the electron pocket implied by quantum oscillation and Hall effect measurements for HgBa2CuO(4+δ) and with corresponding results for YBa2Cu3O(6+δ), which indicates that charge-density-wave correlations are universally responsible for the low-temperature quantum oscillation phenomenon.
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Guarise M, Piazza BD, Berger H, Giannini E, Schmitt T, Rønnow HM, Sawatzky GA, van den Brink J, Altenfeld D, Eremin I, Grioni M. Anisotropic softening of magnetic excitations along the nodal direction in superconducting cuprates. Nat Commun 2014; 5:5760. [DOI: 10.1038/ncomms6760] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Accepted: 11/05/2014] [Indexed: 11/09/2022] Open
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69
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Magnuson M, Schmitt T, Strocov VN, Schlappa J, Kalabukhov AS, Duda LC. Self-doping processes between planes and chains in the metal-to-superconductor transition of YBa2Cu3O6.9. Sci Rep 2014; 4:7017. [PMID: 25388860 PMCID: PMC4228345 DOI: 10.1038/srep07017] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 10/20/2014] [Indexed: 11/08/2022] Open
Abstract
The interplay between the quasi 1-dimensional CuO-chains and the 2-dimensional CuO2 planes of YBa(2)Cu(3)O(6+x) (YBCO) has been in focus for a long time. Although the CuO-chains are known to be important as charge reservoirs that enable superconductivity for a range of oxygen doping levels in YBCO, the understanding of the dynamics of its temperature-driven metal-superconductor transition (MST) remains a challenge. We present a combined study using x-ray absorption spectroscopy and resonant inelastic x-ray scattering (RIXS) revealing how a reconstruction of the apical O(4)-derived interplanar orbitals during the MST of optimally doped YBCO leads to substantial hole-transfer from the chains into the planes, i.e. self-doping. Our ionic model calculations show that localized divalent charge-transfer configurations are expected to be abundant in the chains of YBCO. While these indeed appear in the RIXS spectra from YBCO in the normal, metallic, state, they are largely suppressed in the superconducting state and, instead, signatures of Cu trivalent charge-transfer configurations in the planes become enhanced. In the quest for understanding the fundamental mechanism for high-Tc-superconductivity (HTSC) in perovskite cuprate materials, the observation of such an interplanar self-doping process in YBCO opens a unique novel channel for studying the dynamics of HTSC.
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Weyer J, Jørgensen D, Schmitt T, Maxwell T, Anderson C. Lack of detectable genetic differentiation between den populations of the Prairie Rattlesnake (Crotalusviridis) in a fragmented landscape. CAN J ZOOL 2014. [DOI: 10.1139/cjz-2014-0025] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Numerous studies have reported genetic fragmentation of species whose habitat has been modified by roads and other anthropogenic features, but it is still not clear how most species respond to roads and whether genetic effects can be detected over a limited number of generations. We used road-crossing models and population genetic analysis (based on microsatellite loci) to make inferences about functional connectivity between populations of the Prairie Rattlesnake (Crotalus viridis (Rafinesque, 1818)) on opposite sides of the Trans-Canada Highway near Medicine Hat (Alberta, Canada). The road-crossing model predicted a high probability of mortality while crossing the Trans-Canada Highway. However, model-based genetic clustering methods (STRUCTURE and BAPS) did not detect structure; a nonmodel-based clustering method (DAPC) found structure, but most groups consisted of individuals captured throughout the study area. Estimates of effective population size were immeasurably large and power to detect genic differentiation was diminished if the effective size exceeded 500; this reduction in power was intensified when the number of loci was reduced (from eight to five to account for null alleles). Our results corroborate accounts of long-distance migration by this species and indicate that genetic fragmentation may not be easily detectable over this spatial and temporal scale.
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Schmitt T, de Groot FMF, Rubensson JE. Prospects of high-resolution resonant X-ray inelastic scattering studies on solid materials, liquids and gases at diffraction-limited storage rings. JOURNAL OF SYNCHROTRON RADIATION 2014; 21:1065-76. [PMID: 25177995 PMCID: PMC4151682 DOI: 10.1107/s1600577514017123] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Accepted: 07/24/2014] [Indexed: 05/29/2023]
Abstract
The spectroscopic technique of resonant inelastic X-ray scattering (RIXS) will particularly profit from immensely improved brilliance of diffraction-limited storage rings (DLSRs). In RIXS one measures the intensities of excitations as a function of energy and momentum transfer. DLSRs will allow for pushing the achievable energy resolution, signal intensity and the sampled spot size to new limits. With RIXS one nowadays probes a broad range of electronic systems reaching from simple molecules to complex materials displaying phenomena like peculiar magnetism, two-dimensional electron gases, superconductivity, photovoltaic energy conversion and heterogeneous catalysis. In this article the types of improved RIXS studies that will become possible with X-ray beams from DLSRs are envisioned.
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Plumb NC, Salluzzo M, Razzoli E, Månsson M, Falub M, Krempasky J, Matt CE, Chang J, Schulte M, Braun J, Ebert H, Minár J, Delley B, Zhou KJ, Schmitt T, Shi M, Mesot J, Patthey L, Radović M. Mixed dimensionality of confined conducting electrons in the surface region of SrTiO3. PHYSICAL REVIEW LETTERS 2014; 113:086801. [PMID: 25192117 DOI: 10.1103/physrevlett.113.086801] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2014] [Indexed: 06/03/2023]
Abstract
Using angle-resolved photoemission spectroscopy, we show that the recently discovered surface state on SrTiO(3) consists of nondegenerate t(2g) states with different dimensional characters. While the d(xy) bands have quasi-2D dispersions with weak k(z) dependence, the lifted d(xz)/d(yz) bands show 3D dispersions that differ significantly from bulk expectations and signal that electrons associated with those orbitals permeate the near-surface region. Like their more 2D counterparts, the size and character of the d(xz)/d(yz) Fermi surface components are essentially the same for different sample preparations. Irradiating SrTiO(3) in ultrahigh vacuum is one method observed so far to induce the "universal" surface metallic state. We reveal that during this process, changes in the oxygen valence band spectral weight that coincide with the emergence of surface conductivity are disproportionate to any change in the total intensity of the O 1s core level spectrum. This signifies that the formation of the metallic surface goes beyond a straightforward chemical doping scenario and occurs in conjunction with profound changes in the initial states and/or spatial distribution of near-E(F) electrons in the surface region.
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Gilroy R, Heronemus M, Schmitt T, Moriarty P. Donors With Familial Hypercholesterolemia and Clinical Outcome in Liver Transplant Recipients. Transplantation 2014. [DOI: 10.1097/00007890-201407151-02729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Waller S, Raglow Z, Lemons S, Johnson P, Eid A, Schmitt T, Smothers J, O'Neil M, Gilroy R. Microwave ablation of a large renal aspergilloma. Transpl Infect Dis 2014; 16:496-500. [DOI: 10.1111/tid.12221] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 12/19/2013] [Accepted: 01/08/2014] [Indexed: 11/28/2022]
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Bisogni V, Kourtis S, Monney C, Zhou K, Kraus R, Sekar C, Strocov V, Büchner B, van den Brink J, Braicovich L, Schmitt T, Daghofer M, Geck J. Femtosecond dynamics of momentum-dependent magnetic excitations from resonant inelastic X-ray scattering in CaCu2O3. PHYSICAL REVIEW LETTERS 2014; 112:147401. [PMID: 24766010 DOI: 10.1103/physrevlett.112.147401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Indexed: 06/03/2023]
Abstract
Taking spinon excitations in the quantum antiferromagnet CaCu2O3 as an example, we demonstrate that femtosecond dynamics of magnetic electronic excitations can be probed by direct resonant inelastic x-ray scattering (RIXS). To this end, we isolate the contributions of single and double spin-flip excitations in experimental RIXS spectra, identify the physical mechanisms that cause them, and determine their respective time scales. By comparing theory and experiment, we find that double spin flips need a finite amount of time to be generated, rendering them sensitive to the core-hole lifetime, whereas single spin flips are, to a very good approximation, independent of it. This shows that RIXS can grant access to time-domain dynamics of excitations and illustrates how RIXS experiments can distinguish between excitations in correlated electron systems based on their different time dependence.
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