Green's function variational approach to orbital polarons in KCuF3

Abstract

We develop an $e_g$ orbital, $t$-$J$-like model of a single charge doped into a two-dimensional plane with ferromagnetic spin order and alternating orbital order, and present its solution by Green's functions in the variational approximation framework. The model is designed to represent the orbital physics within ferromagnetic $(a,b)$ planes of KCuF${}_3$ and K${}_2$CuF${}_4$. The variational approximation (VA) relies on the systematic generation of equations of motion for the Green's function, taking into account the real-space constraints coming from the exclusion of doubly occupied sites. This method is compared to the firmly established self-consistent Born approximation, and to the variational cluster approximation (VCA) which relies on the itinerant regime of the model. We find that the present variational approximation captures the essential aspects of the spectral weight distribution of the coherent quasiparticle state and gives a result similar to the VCA, while also reproducing well the momentum dependence of the spectral moments. In contrast, the spectral function obtained within the self-consistent Born approximation is more incoherent and its quasiparticle is heavier, at strong effective couplings, than observed with VCA and VA.

14 pages, 9 figures

References in corpus (28)

• Orbital order and possible superconductivity in LaNiO3/LaMO3 superlattices
• Spin-orbital frustrations and anomalous metallic state in iron-pnictide superconductors
• Variational cluster approach to correlated electron systems in low dimensions
• Spin-orbital quantum liquid on the honeycomb lattice
• Variational cluster approach to spontaneous symmetry breaking: The itinerant antiferromagnet in two dimensions
• Green's function of a dressed particle
• The Green's Function of the Holstein Polaron
• Spin-Orbital Entanglement and Violation of the Goodenough-Kanamori Rules
• Fingerprints of spin-orbital entanglement in transition metal oxides
• Theory of optical spectral weights in Mott insulators with orbital degrees of freedom
• Absence of Hole Confinement in Transition Metal Oxides with Orbital Degeneracy
• The dynamics of a doped hole in cuprates is not controlled by spin fluctuations
• Orbital liquid in ferromagnetic manganites: The orbital Hubbard model for $e_g$ electrons
• Spectral properties of orbital polarons in Mott insulators
• Noncollinear Magnetic Order Stabilized by Entangled Spin-Orbital Fluctuations
• Ferro-Orbitally Ordered Stripes in Systems with Alternating Orbital Order
• Von Neumann Entropy Spectra and Entangled Excitations in Spin-Orbital Models
• Spin-Orbital Order Modified by Orbital Dilution in Transition Metal Oxides: From Spin Defects to Frustrated Spins Polarizing Host Orbitals
• Orbital ordering in e_g orbital systems: Ground states and thermodynamics of the 120 degree model
• Doping dependence of spin and orbital correlations in layered manganites
• Exotic spin orders driven by orbital fluctuations in the Kugel-Khomskii model
• Entangled spin-orbital phases in the bilayer Kugel-Khomskii model
• Exploring the spin-orbital ground state of Ba3CuSb2O9
• Defect states and spin-orbital physics in doped vanadates Y1-xCaxVO3
• Frustration and Entanglement in Compass and Spin-Orbital Models
• Dilution effect in correlated electron system with orbital degeneracy
• Striped critical spin liquid in a spin-orbital entangled RVB state in a projected entangled-pair state representation
• Hole propagation in the orbital compass models

Cited by in corpus (2)

• Orbiton-magnon interplay in the spin-orbital polarons of KCuF3 and LaMnO3
• The Green function variational approximation: Significance of physical constraints