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TT: Fachverband Tiefe Temperaturen
TT 30: Superconductivity - Poster Session
TT 30.25: Poster
Montag, 31. März 2014, 15:00–19:00, P2
Manifestation of nematic degrees of freedom in the Raman response of pnictides — •Una Karahasanovic and Joerg Schmalian — Karlsruher Institut für Technologie, Wolfgang-Gaede-Str. 1 D-76131 Karlsruhe
The electronic nematic phase in pnictides, characterized by the broken C4 symmetry, is believed to be generated by the presence of magnetic fluctuations associated with the striped phase [1], and occurs above the magnetic transition temperature. Detecting the presence of nematic fluctuations in iron-based superconductors is a difficult task, since it involves measuring four spin correlation functions. So far, these fluctuations were detected through the changes that they induce in the shear modulus (since the nematic order parameter couples to the orthorombic distortion). The presence of nematic fluctuations is felt even above the nematic transition, i.e. in the tetragonal phase.
Nematic degrees of freedom also manifest themeselves in the experimentally measurable Raman response function, which is a density-density correlation weighted by an appropriate form factor [2, 3]. We calculate the lineshape of the Raman response function in the tetragonal phase by considering Aslamazov-Larkin type of diagrams. We show that the reponse vanishes for the B2g symmetry of the form factor, but not for the B1g symmetry, as observed in the experiment.
R. Fernandes and J. Schmalian, Supercond. Sci. Technol. 25, 084005 (2012).
Y. Gallais et al, arXiv:1302.6255 (2013).
S. Caprara et al, Phys. Rev. Lett. 95, 117004 (2005).