Abstract
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.
Highlights
The absence of an accepted theory for superconductivity in cuprates has recently resulted in calls for new ideas [1,2]
We provide a deeper understanding of the regimes where small polarons are formed and when they are allowed to tunnel in the form of an internal quantum tunneling polarons (IQTPs) as a function of the electron-phonon coupling, λ, and the Kuramoto–anharmonic coupling, K
We restricted our analysis to a reduced cluster built to represent a much richer crystallographic environment of cuprate superconductors, in this work, we have included two novel features: (i) the planar O pl bridging the two Cu − Oap pairs and (ii) the structural anharmonicity related to the coupling within the dielectric layer, explored by the dynamical analysis based on the Kuramoto model
Summary
The absence of an accepted theory for superconductivity in cuprates has recently resulted in calls for new ideas [1,2]. Matter 2021, 6, 52 from X-ray absorption fine structure (XAFS), inelastic neutron scattering (INS) and inelastic. X-ray scattering (IXS), Raman spectroscopy (RS), infrared absorption spectroscopy (IR), time-resolved optical spectroscopy and nonlinear magnetic response measurements [4,5,6,7,8,9,10,11,12,13]. Have pointed to an inhomogeneous ground state in different hole-doped cuprates as a precursor to the superconducting phase. Anomalous isotopic effects [14] and shortrange structural fluctuations [15] are among the manifestations of this inhomogeneity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
