Finite-cluster study of superconductivity in the two-dimensional molecular-crystal model

Journal Article · Wed May 01 00:00:00 EDT 1991 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.43.10413· OSTI ID:5461636

Levine, G; Su, W P ^[1]

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1. Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204-5504 (USA)

We study the singlet pairing and charge-density-wave (CDW) instabilities in the two-dimensional molecular-crystal model using diagrammatic perturbation theory and nonperturbative fermion Monte Carlo (MC) methods applied to a 36-site cluster. Migdal-Eliashberg strong-coupling theory is used to calculate susceptibilities above {ital T}{sub {ital c}} and to calculate the temperature-dependent gap function below {ital T}{sub {ital c}}. These computations are performed with bare phonons as well as renormalized ones, and for a range of doping concentrations spanning the CDW phase transition. We find close agreement between the pairing susceptibility calculated within the strong-coupling approximation using bare phonons and susceptibility calculated by the fermion Monte Carlo technique. Using the above- and below-{ital T}{sub {ital c}} strong-coupling calculations as a guide, we argue that the fermion MC computation indicates a superconducting ground state with the highest transition temperature occurring at a doping concentration close to the CDW phase boundary. The increase in {ital T}{sub {ital c}} is attributed mostly to the logarithmic singularity in the density of states at half-filling. Phonon softening seems to have only a small effect according to the nonperturbative treatment.

• OSTI ID: 5461636
• Journal Information: Physical Review, B: Condensed Matter; (USA), Vol. 43:13; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
SUPERCONDUCTORS
ENERGY GAP
PAIRING INTERACTIONS
CHARGE DENSITY
CORRELATION FUNCTIONS
CRYSTAL MODELS
FEYNMAN DIAGRAM
GORKOV-ELIASHBERG THEORY
MONTE CARLO METHOD
PERTURBATION THEORY
PHONONS
TEMPERATURE DEPENDENCE
TWO-DIMENSIONAL CALCULATIONS
DIAGRAMS
FUNCTIONS
INTERACTIONS
MATHEMATICAL MODELS
QUASI PARTICLES
656100* - Condensed Matter Physics- Superconductivity