Abstract
We use scanning tunneling microscopy to determine the surface structure and dopant distribution in Pr${}_{x}$Ca${}_{1\ensuremath{-}x}$Fe${}_{2}$As${}_{2}$, the highest-${T}_{c}$ member of the 122 family of iron-based superconductors. We identify the cleaved surface termination by mapping the local tunneling barrier height, related to the work function. We image the individual Pr dopants responsible for superconductivity, and show that they do not cluster, but in fact repel each other at short length scales. We therefore suggest that the low volume fraction high-${T}_{c}$ superconducting phase is unlikely to originate from Pr inhomogeneity.
Highlights
We use scanning tunneling microscopy to determine the surface structure and dopant distribution in PrxCa1−xFe2As2, the highest-Tc member of the 122 family of iron-based superconductors
In the first generation of AFe2As2 C (122) Fe-based superconductors (Fe-SCs), hole doping resulted in higher maximum B Tc (38 K in KxBa1−xFe2As2 [3]) than electron dopI ing (25 K in Ba(Fe1−xCox)2As2 [4])
E D ever, the high Tc appeared in only ∼ 10% of the volume, while the bulk of the material showed Tc ∼ 10 − 20 K
Summary
We use scanning tunneling microscopy to determine the surface structure and dopant distribution in PrxCa1−xFe2As2, the highest-Tc member of the 122 family of iron-based superconductors. Nanoscale Surface Element Identification and Dopant Homogeneity in the High-Tc Superconductor PrxCa1−xFe2As2
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