Tuesday, July 30, 2013

1307.7676 (G. Karakonstantakis et al.)

Correlations and Renormalization of the Electron-Phonon Coupling in the
Honeycomb Hubbard Ladder and Superconductivity in Polyacene

G. Karakonstantakis, L. Liu, R. Thomale, S. A. Kivelson
We have performed extensive density matrix renormalization group (DMRG) studies of the Hubbard model on a honeycomb ladder. The band structure (with Hubbard U=0) exhibits an unusual quadratic band touching at half filling, which is associated with a quantum Lifshitz transition from a band insulator to a metal. %SAK as a function of a third-neighbor hopping parameter. For one electron per site, non-zero $U$ drives the system into an insulating state in which there is no pair-binding between added electrons; this implies that superconductivity driven directly by the repulsive electron-electron interactions is unlikely in the regime of small doping, $x\ll 1$. However, the divergent density of states as $x\to 0$, the large values of the phonon frequencies, and an unusual correlation induced enhancement of the electron-phonon coupling imply that lightly doped polyacenes, which approximately realize this structure, are good candidates for high temperature electron-phonon driven superconductivity.
View original: http://arxiv.org/abs/1307.7676

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