Nanoscale Surface Element Identification and Dopant Homogeneity in the High-$T_c$ Superconductor Pr${}_x$Ca${}_{1-x}$Fe${}_2$As${}_2$

Abstract

We use scanning tunneling microscopy to determine the surface structure and dopant distribution in Pr${}_x$Ca${}_{1-x}$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.

5 pages, 4 figures

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• Surface terminations and layer-resolved spectroscopy in 122 iron pnictide superconductors
• Evidence for Defect-induced Superconductivity up to 49 K in (Ca1-xRx)Fe2As2
• Pairing insights in iron-based superconductors from scanning tunneling microscopy
• Separation of antiferromagnetism and high-temperature superconductivity in Ca${}_{1-x}$La${}_x$Fe${}_2$As${}_2$ under pressure
• Why is the superconducting Tc so high in rare-earth-doped CaFe2As2?
• Effect of surface morphology and magnetic impurities on the electronic structure in cobalt-doped BaFe2As2 superconductors
• Low work function in the 122-family of iron-based superconductors
• Probing Image Potential States on Topological Semimetal Antimony Surface
• Phase Diagram and Weak-link Behavior in Nd-doped CaFe_2As_2
• Drastic electronic structure reconstruction of Ca${}_{1-x}$Pr${}_x$Fe${}_2$As${}_2$ in the collapsed tetragonal phase
• Electronic inhomogeneities in the superconducting phase of CaFe1.96Ni0.04As2 single crystals
• Influence of growth flux solvent on anneal-tuning of ground states in CaFe2As2