Symmetry 2012, 4(1), 251-264; doi:10.3390/sym4010251
Article

One-Sign Order Parameter in Iron Based Superconductor

1,* email, 1email, 1,2email, 1email, 1,3email, 4email, 5email and 1email
Received: 2 March 2012; in revised form: 14 March 2012 / Accepted: 16 March 2012 / Published: 21 March 2012
(This article belongs to the Special Issue Symmetries of Electronic Order)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: The onset of superconductivity at the transition temperature is marked by the onset of order, which is characterized by an energy gap. Most models of the iron-based superconductors find a sign-changing (s±) order parameter [1–6], with the physical implication that pairing is driven by spin fluctuations. Recent work, however, has indicated that LiFeAs has a simple isotropic order parameter [7–9] and spin fluctuations are not necessary [7,10], contrary to the models [1–6]. The strength of the spin fluctuations has been controversial [11,12], meaning that the mechanism of superconductivity cannot as yet be determined. We report the momentum dependence of the superconducting energy gap, where we find an anisotropy that rules out coupling through spin fluctuations and the sign change. The results instead suggest that orbital fluctuations assisted by phonons [13,14] are the best explanation for superconductivity.
Keywords: iron-based superconductors; ARPES; LiFeAs; order parameter
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MDPI and ACS Style

Borisenko, S.V.; Zabolotnyy, V.B.; Kordyuk, A.A.; Evtushinsky, D.V.; Kim, T.K.; Morozov, I.V.; Follath, R.; Büchner, B. One-Sign Order Parameter in Iron Based Superconductor. Symmetry 2012, 4, 251-264.

AMA Style

Borisenko SV, Zabolotnyy VB, Kordyuk AA, Evtushinsky DV, Kim TK, Morozov IV, Follath R, Büchner B. One-Sign Order Parameter in Iron Based Superconductor. Symmetry. 2012; 4(1):251-264.

Chicago/Turabian Style

Borisenko, Sergey V.; Zabolotnyy, Volodymyr B.; Kordyuk, Alexnader A.; Evtushinsky, Danil V.; Kim, Timur K.; Morozov, Igor V.; Follath, Rolf; Büchner, Bernd. 2012. "One-Sign Order Parameter in Iron Based Superconductor." Symmetry 4, no. 1: 251-264.

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