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Kinks and d-waves from phonons: the intermediate coupling story

Hague, J. P. (2008). Kinks and d-waves from phonons: the intermediate coupling story. Journal of Physics and Chemistry of Solids, 69(12) pp. 2982–2985.

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I present results from an approach that extends the Eliashberg theory by systematic expansion in the vertex function; an essential extension at large phonon frequencies, even for weak coupling. In order to deal with computationally expensive double sums over momenta, a dynamical cluster approximation (DCA) approach is used to incorporate momentum dependence into the Eliashberg equations. First, I consider the effects of introducing partial momentum dependence on the standard Eliashberg theory using a quasi-local approximation; which I use to demonstrate that it is essential to include corrections beyond the standard theory when investigating d-wave states. Using the extended theory with vertex corrections, I compute electron and phonon spectral functions. A kink in the electronic dispersion is found in the normal state along the major symmetry directions, similar to that found in photo-emission from cuprates. The phonon spectral function shows that for weak coupling Wλ<ω0, the dispersion for phonons has weak momentum dependence, with consequences for the theory of optical phonon mediated d-wave superconductivity, which is shown to be 2nd order in λ. In particular, examination of the order parameter vs. filling shows that vertex corrections lead to d-wave superconductivity mediated via simple optical phonons. I map out the order parameters in detail, showing that there is significant induced anisotropy in the superconducting pairing in quasi-2D systems.

Item Type: Journal Item
Copyright Holders: 2008 Elsevier Ltd
ISSN: 0022-3697
Project Funding Details:
Funded Project NameProject IDFunding Body
Not SetEP/C518365/1EPSRC (Engineering and Physical Sciences Research Council)
Keywords: extended Eliashberg Theory; superconductivity; spectroscopy; unconventional pairing
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Research Group: Physics
Item ID: 12865
Depositing User: Astrid Peterkin
Date Deposited: 19 Jan 2009 08:14
Last Modified: 07 Dec 2018 09:15
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