Evidence for domain wall superconductivity in antiferromagnetic CaFe2As2
ORAL
Abstract
$^{75}$As nuclear magnetic resonance (NMR), resistivity, and magnetization measurements in the antiferromagnetic state of the iron-based superconductor parent compound CaFe$_2$As$_2$ exhibit anomalous features consistent with the collective freezing of domain walls. Below T* $\approx$ 10 K, the $^{75}$As NMR measurements reveal the presence of slow fluctuations of the hyperfine field, the resistivity shows an enhancement and subsequent suppression, and the bulk magnetization shows a sharp increase. These features in both the charge and spin response are strongly field dependent, are fully suppressed by H* $\approx$ 15 T, and suggest the presence of filamentary superconductivity nucleated at the antiphase domain walls.
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