Hague, J. P.
|DOI (Digital Object Identifier) Link:||http://dx.doi.org/10.1016/j.jpcs.2008.06.105|
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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 Article|
|Copyright Holders:||2008 Elsevier Ltd|
|Project Funding Details:||
|Keywords:||extended Eliashberg Theory; superconductivity; spectroscopy; unconventional pairing|
|Academic Unit/Department:||Science > Physical Sciences
|Interdisciplinary Research Centre:||Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Biomedical Research Network (BRN)
|Depositing User:||Astrid Peterkin|
|Date Deposited:||19 Jan 2009 08:14|
|Last Modified:||14 Jan 2016 17:35|
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