Anharmonic polaronic model and high-[ital T][sub [ital c]] superconductivity

Journal Article · Tue Jun 01 04:00:00 EDT 1993 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.47.14425· OSTI ID:6769524

Konior, J ^[1]

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1. Institute of Physics, Jagellonian University, PL-30059 Krakow, Reymonta 4 (Poland)

An anharmonic polaronic model is considered. The model consists of the electronic subsystem, described within the extended Hubbard model, coupled to anharmonic local phonons. The canonical-variable-displacement Holstein-Lang-Firsov transformation is used for shifting the phononic coordinate system in order to minimize the energy of the phonons. Then, the effective electronic Hamiltonian is obtained by averaging over the ground state of the phononic subsystem. It is shown that anharmonicity introduces two main additional factors as compared with the harmonic case. First, the band-narrowing factor is a less rapidly decaying function of the electron-phonon interaction strength. Second, anharmonicity introduces further renormalization of the on-site and intersite interaction between fermions. Implications for the application of the polaronic model to the high-[ital T][sub [ital c]] systems are twofold. Due to the first factor, higher values of the electron-phonon coupling are allowed without making polarons too heavy as compared with the experimental value of the effective mass in these materials. Second, small anharmonically induced renormalizations may or may not favor superconductivity. Combination of these two effects leads generally to the effective electronic Hamiltonian that yields more favorable conditions for superconductivity to occur than in the harmonic case.

• OSTI ID: 6769524
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 47:21; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

665411* -- Basic Superconductivity Studies-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANHARMONIC CRYSTALS
COUPLING
CRYSTAL MODELS
CRYSTALS
ELECTRON-PHONON COUPLING
ENERGY LEVELS
GROUND STATES
HAMILTONIANS
HIGH-TC SUPERCONDUCTORS
HUBBARD MODEL
MATHEMATICAL MODELS
MATHEMATICAL OPERATORS
PHONONS
POLARONS
QUANTUM OPERATORS
QUASI PARTICLES
RENORMALIZATION
SUPERCONDUCTORS