What is the true charge transfer gap in parent insulating cuprates?

Abstract

A large body of experimental data point towards a charge transfer instability of parent insulating cuprates to be their unique property. We argue that the true charge transfer gap in these compounds is as small as 0.4-0.5\,eV rather than 1.5-2.0\,eV as usually derived from the optical gap measurements. In fact we deal with a competition of the conventional (3d${}^9$) ground state and a charge transfer (CT) state with formation of electron-hole dimers which evolves under doping to an unconventional bosonic system. Our conjecture does provide an unified standpoint on the main experimental findings for parent cuprates including linear and nonlinear optical, Raman, photoemission, photoabsorption, and transport properties anyhow related with the CT excitations. In addition we suggest a scenario for the evolution of the CuO${}_2$ planes in the CT unstable cuprates under a nonisovalent doping.

13 pages, 5 figures, submitted to PRB

References in corpus (5)

• Quantum phase transition from a superfluid to a Mott insulator in a gas of ultracold atoms
• Inelastic Light Scattering From Correlated Electrons
• Anomalous High-Energy Spin Excitations in La2CuO4
• Observation of a 500meV Collective Mode in La${}_{2-x}$Sr${}_x$CuO${}_4$ and Nd${}_2$CuO${}_4$
• Strong charge fluctuations manifested in the high-temperature Hall coefficient of high-T_c cuprates

Cited by in corpus (26)

• Superconductivity in nickel based 112 systems
• Unusual X-ray excited luminescence spectra of NiO suggestive of a self-trapping of the d-d charge transfer exciton
• Electron-Phonon-Driven Three-Dimensional Metallicity in an Insulating Cuprate
• Perspectives of the disproportionation driven superconductivity in strongly correlated 3d compounds
• Effective-field theory for high-$T_c$ cuprates
• Computational study of antiferromagnetic and mixed-valent diamagnetic phase of AgF2: crystal, electronic and phonon structure and p-T phase diagram
• Phase diagrams of a 2D Ising spin-pseudospin model
• Topological structures in unconventional scenario for 2D cuprates
• Critical temperatures of a model cuprate
• Model of charge triplets for high-T${}_c$ cuprates
• Pseudo-transition between antiferromagnetic and charge orders in a minimal spin-pseudospin model of one-dimensional cuprates
• Pseudotransitions in a dilute Ising chain
• Hubbard-model description of the high-energy spin-spectral-weight distribution in La(2)CuO(4)
• A three-state model with competing antiferromagnetic and pairing interactions
• The MFA ground states for the extended Bose-Hubbard model with a three-body constraint
• Pseudospin S=1 description of the cuprate complexity: the charge triplets model
• Phase separation in high-T${}_c$ cuprates
• Competition between the Spin and Pseudospin Subsystems in a Model Cuprate
• Insulator-bad metal transition in RNiO${}_3$ nickelates beyond Hubbard model and density functional theory
• Critical properties of a 2D frustrated magnet with non-magnetic impurities
• Asymptotics of quasi-classical localized states in 2D system of charged hard-core bosons
• Superconductivity in model cuprate as an S=1 pseudomagnon condensation
• Nontrivial Ground State Degeneracy of the Spin-Pseudospin Model of a Two-Dimensional Magnet Near the Frustration Point
• `Interaction annealing' to determine effective quantized valence and orbital structure: an illustration with ferro-orbital order in WTe${}_2$
• Spin-spectral-weight distribution and energy range of the parent compound La${}_2$CuO${}_4$
• Predicting parameters of a model cuprate superconductor using machine learning