Speakers: Alexander V. Boris (Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany)
Place: Přednáškový sál Fyzikálního ústavu AV ČR Na Slovance
Presented in English
Organisers:
Department of Dielectrics
By combining the unique infrared imaging capabilities and nanoscale resolution of the scattering-type scanning near-field optical microscopy (s-SNOM) with bulk sensitivity at variable depth of low-energy muon spin rotation (LE-mSR) we determined the geometry and magnitude of the phase separation in nearly-stoichiometric superconducting Rb2Fe4Se5 single crystals with Tc = 32 K [1]. The paramagnetic domains were found to have a shape of thin metallic sheets parallel to the iron-selenide plane with a characteristic size of only several nanometers out of plane but up to 10 μm in plane. The intrinsic nanoscale layering of the metallic and insulating phases is confirmed by the effective-medium in-plane [2] and out-of-plane dielectric response studied by infrared ellipsometry in a combination with time-domain THz transmission spectroscopy. By means of LE-μSR we further show that the antiferromagnetic semiconducting phase occupies ~ 80% of the sample volume in the bulk and is strongly weakened near the surface. These results have important implications for the interpretation of bulk- and surface-sensitive measurements on Rb2Fe4Se5, and for the understanding of the interplay between superconductivity and antiferromagnetism in this material.
[1] A. Charnukha et al., Phys. Rev. B 85 100504R (2012).
[2] A. Charnukha et al., subm. to PRL, Preprint at http://arxiv.org/abs/1202.5446 (2012).
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