Reverse Monte Carlo study of Cu—O bond distortions in YBa2Cu3O6.9

Young, Callum A.; Dixon, Edward; Tucker, Matthew G.; Keen, David A.; Hayward, Michael A.; Goodwin, Andrew L.

doi:10.1524/zkri.2012.1503

Cited by 5 publications

(5 citation statements)

References 36 publications

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“…This methodology has demonstrated its effectiveness in elucidating the structure of amorphous and poorly crystalline materials using total scattering PDF data. 37,38 The Pd metal phase factor (X Pd ) is very low indicating, within experimental uncertainty, the likely absence of any Pd metallic phase. The PdO structure and relative concentration is maintained at 700 1C where the fit (R w = 32%) is similar to that for Pd-RT data.…”

Section: Resultsmentioning

confidence: 90%

Elucidation of structure and nature of the PdO–Pd transformation using in situ PDF and XAS techniques

Keating

Sankar

Hyde

et al. 2013

Phys. Chem. Chem. Phys.

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The PdO-Pd phase transformation in a 4 wt% Pd/Al2O3 catalyst has been investigated using in situ X-ray absorption spectroscopy (XAS) and in situ X-ray total scattering (also known as high-energy X-ray diffraction) techniques. Both the partial and total pair distribution functions (PDF) from these respective techniques have been analysed in depth. New information from PDF analysis of total scattering data has been garnered using the differential PDF (d-PDF) approach where only correlations orginating from PdO and metallic Pd are extracted. This method circumvents problems encountered in characerising the catalytically active components due to the diffuse scattering from the disordered γ-Al2O3 support phase. Quantitative analysis of the palladium components within the catalyst allowed for the phase composition to be established at various temperatures. Above 850 °C it was found that PdO had converted to metallic Pd, however, the extent of reduction was of the order ca. 70% Pd metal and 30% PdO. Complementary in situ XANES and EXAFS were performed, with heating to high temperature and subsequent cooling in air, and the results of the analyses support the observations, that residual PdO is detected at elevated temperatures. Hysteresis in the transformation upon cooling is confirmed from XAS studies where reoxidation occurs below 680 °C.

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Section: Resultsmentioning

confidence: 90%

Elucidation of structure and nature of the PdO–Pd transformation using in situ PDF and XAS techniques

Keating

Sankar

Hyde

et al. 2013

Phys. Chem. Chem. Phys.

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“…EXAFS therefore accesses time and energy scales corresponding to collective dynamical phenomena (25,38,39). Dynamical structures such as the iqtp are demonstrated when S(Q, E/t = 0) gives locations for atoms that differ from those (19,38) obtained from diffraction and elastic scattering measurements (20)(21)(22)40). This complementarity was the basis for the original Fig.…”

Section: Significancementioning

confidence: 96%

Nonadiabatic coupling of the dynamical structure to the superconductivity in YSr ₂ Cu _2.75 Mo _0.25 O _7.54 and Sr ₂ CuO _3.3

Conradson

Geballe

Jin

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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A crucial issue in cuprates is the extent and mechanism of the coupling of the lattice to the electrons and the superconductivity. Here we report Cu K edge extended X-ray absorption fine structure measurements elucidating the internal quantum tunneling polaron (iqtp) component of the dynamical structure in two heavily overdoped superconducting cuprate compounds, tetragonal YSr2Cu2.75Mo0.25O7.54 with superconducting critical temperature, Tc = 84 K and hole density p = 0.3 to 0.5 per planar Cu, and the tetragonal phase of Sr2CuO3.3 with Tc = 95 K and p = 0.6. In YSr2Cu2.75Mo0.25O7.54 changes in the Cu-apical O two-site distribution reflect a sequential renormalization of the double-well potential of this site beginning at Tc, with the energy difference between the two minima increasing by ∼6 meV between Tc and 52 K. Sr2CuO3.3 undergoes a radically larger transformation at Tc, >1-Å displacements of the apical O atoms. The principal feature of the dynamical structure underlying these transformations is the strongly anharmonic oscillation of the apical O atoms in a double-well potential that results in the observation of two distinct O sites whose Cu–O distances indicate different bonding modes and valence-charge distributions. The coupling of the superconductivity to the iqtp that originates in this nonadiabatic coupling between the electrons and lattice demonstrates an important role for the dynamical structure whereby pairing occurs even in a system where displacements of the atoms that are part of the transition are sufficiently large to alter the Fermi surface. The synchronization and dynamic coherence of the iqtps resulting from the strong interactions within a crystal would be expected to influence this process.

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“…In particular, inelastic neutron scattering [16,17] and X-ray absorption spectroscopy [18], which are sensitive to the dynamic structure [19,20], revealed two-site distributions of certain Cu-apical O pairs [21][22][23][24]. Since the static structure determined by crystallography only identified single positions for these atoms [25], a proposed interpretation of these anomalous pairs was that they were the result of the oxygen atoms and their associated charges undergoing quantum tunneling between the two sites [3,19,20,26]. In addition, the difference between the two Cu-O distances indicated that these sites were associated with different charges on the oxygen.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Charge-Lattice Dynamics across the Kuramoto Synchronization Phase Diagram of Quantum Tunneling Polarons in Cuprate Superconductors

et al. 2021

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Because of its sensitivity to the instantaneous structure factor, S(Q,t = 0), Extended X-ray Absorption Fine Structure (EXAFS) is a powerful tool for probing the dynamic structure of condensed matter systems in which the charge and lattice dynamics are coupled. When applied to hole-doped cuprate superconductors, EXAFS has revealed the presence of internal quantum tunneling polarons (IQTPs). An IQTP arises in EXAFS as a two-site distribution for certain Cu–O pairs, which is also duplicated in inelastic scattering but not observed in standard diffraction measurements. The Cu–Sr pair distribution has been found to be highly anharmonic and strongly correlated to both the IQTPs and to superconductivity, as, for example, in YSr2Cu2.75Mo0.25O7.54(Tc=84 K). In order to describe such nontrivial, anharmonic charge-lattice dynamics, we have proposed a model Hamiltonian for a prototype six-atom cluster, in which two Cu-apical-O IQTPs are charge-transfer bridged through Cu atoms by an O atom in the CuO2 plane and are anharmonically coupled via a Sr atom. By applying an exact diagonalization procedure to this cluster, we have verified that our model indeed produces an intricate interplay between charge and lattice dynamics. Then, by using the Kuramoto model for the synchronization of coupled quantum oscillators, we have found a first-order phase transition for the IQTPs into a synchronized, phase-locked phase. Most importantly, we have shown that this transition results specifically from the anharmonicity. Finally, we have provided a phase diagram showing the onset of the phase-locking of IQTPs as a function of the charge-lattice and anharmonic couplings in our model. We have found that the charge, initially confined to the apical oxygens, is partially pumped into the CuO2 plane in the synchronized phase, which suggests a possible connection between the synchronized dynamic structure and high-temperature superconductivity (HTSC) in doped cuprates.

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Reverse Monte Carlo study of Cu—O bond distortions in YBa₂Cu₃O_6.9

Cited by 5 publications

References 36 publications

Elucidation of structure and nature of the PdO–Pd transformation using in situ PDF and XAS techniques

Elucidation of structure and nature of the PdO–Pd transformation using in situ PDF and XAS techniques

Nonadiabatic coupling of the dynamical structure to the superconductivity in YSr ₂ Cu _2.75 Mo _0.25 O _7.54 and Sr ₂ CuO _3.3

Evolution of Charge-Lattice Dynamics across the Kuramoto Synchronization Phase Diagram of Quantum Tunneling Polarons in Cuprate Superconductors

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Reverse Monte Carlo study of Cu—O bond distortions in YBa2Cu3O6.9

Cited by 5 publications

References 36 publications

Elucidation of structure and nature of the PdO–Pd transformation using in situ PDF and XAS techniques

Elucidation of structure and nature of the PdO–Pd transformation using in situ PDF and XAS techniques

Nonadiabatic coupling of the dynamical structure to the superconductivity in YSr 2 Cu 2.75 Mo 0.25 O 7.54 and Sr 2 CuO 3.3

Evolution of Charge-Lattice Dynamics across the Kuramoto Synchronization Phase Diagram of Quantum Tunneling Polarons in Cuprate Superconductors

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Reverse Monte Carlo study of Cu—O bond distortions in YBa₂Cu₃O_6.9

Nonadiabatic coupling of the dynamical structure to the superconductivity in YSr ₂ Cu _2.75 Mo _0.25 O _7.54 and Sr ₂ CuO _3.3