Talk (non-conference) (Invited)

FZJ-2021-00704

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Structure, magnetism, and superconductivity in Fe-based superconductors

Nandi, S. (Corresponding author)FZJ*

2021

Abstract: In iron-based high-temperature superconductors, magnetic fluctuations and magneto-elastic effects are believed to be important for the superconducting electron pairing mechanism. To gain insight into the interplay between the different ordering phenomena and the underlying couplings we studied the magnetic order and lattice distortion on AFe2As2 (A = Ca, Sr, Ba, Eu) single crystals by neutron and x-ray diffraction. High-resolution x-ray diffraction and neutron scattering measurements reveal an unusually strong response of the lattice and ordered magnetic moment to superconductivity in Co-doped BaFe2As2. We propose that the coupling between lattice and superconductivity is indirect and arises due to the magnetoelastic coupling, in the form of emergent nematic order, and the strong competition between the magnetism and superconductivity. In contrast to the coexistence of superconductivity and antiferromagnetism in the Co-doped “122” sample, we show that the superconductivity and ferromagnetism coexist in the P-doped Eu based “122” Fe-pnictides. Coexistence between these two antagonistic phenomena are puzzling but can be explained in terms of the formation of a spontaneous vortex state.

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Contributing Institute(s):

1. Streumethoden (JCNS-2)
2. Streumethoden (PGI-4)
3. JARA-FIT (JARA-FIT)

Research Program(s):

1. 6G4 - Jülich Centre for Neutron Research (JCNS) (POF3-623) (POF3-623)
2. 632 - Materials – Quantum, Complex and Functional Materials (POF4-632) (POF4-632)

Appears in the scientific report 2021

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