標題: Covariant gaussian approximation in Ginzburg-Landau model
作者: Wang, J. F.
Li, D. P.
Kao, H. C.
Rosenstein, B.
電子物理學系
Department of Electrophysics
關鍵字: Covariant gaussian approximation;Ginzburg-Landau;Ward identity;Superconducting thermal fluctuations;Magnetic penetration depth
公開日期: 1-May-2017
摘要: Condensed matter systems undergoing second order transition away from the critical fluctuation region are usually described sufficiently well by the mean field approximation. The critical fluctuation region, determined by the Ginzburg criterion, vertical bar T/T-c, 1 vertical bar << Gi, is narrow even in high T, superconductors and has universal features well captured by the renormalization group method. However recent experiments on magnetization, conductivity and Nernst effect suggest that fluctuations effects are large in a wider region both above and below T-c. In particular some "pseudogap" phenomena and strong renormalization of the mean field critical temperature T-mf can be interpreted as strong fluctuations effects that are nonperturbative (cannot be accounted for by "gaussian fluctuations"). The physics in a broader region therefore requires more accurate approach. Self consistent methods are generally "non-conserving" in the sense that the Ward identities are not obeyed. This is especially detrimental in the symmetry broken phase where, for example, Goldstone bosons become massive. Covariant gaussian approximation remedies these problems. The Green's functions obey all the Ward identities and describe the fluctuations much better. The results for the order parameter correlator and magnetic penetration depth of the Ginzburg-Landau model of superconductivity are compared with both Monte Carlo simulations and experiments in high T-c, cuprates. (C) 2017 Elsevier Inc. All rights reserved.
URI: http://dx.doi.org/10.1016/j.aop.2017.03.015
http://hdl.handle.net/11536/145487
ISSN: 0003-4916
DOI: 10.1016/j.aop.2017.03.015
期刊: ANNALS OF PHYSICS
Volume: 380
起始頁: 228
結束頁: 254
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