Superconductivity at 15.6 K in Calcium-doped Tb_{1-x}Ca_xFeAsO: the structure requirement for achieving superconductivity in the hole-doped 1111 phase

TL;DR

This study reports superconductivity at 15.6 K in calcium-doped TbFeAsO, highlighting the importance of ion size and structure for hole-doped 1111 phase superconductivity, with detailed analysis of doping effects and charge carriers.

Contribution

It demonstrates that calcium doping induces superconductivity in TbFeAsO and identifies ion size as a key structural requirement for hole-doped 1111 phase superconductivity.

Findings

Superconductivity at 15.6 K achieved in Tb_{1-x}Ca_xFeAsO.

Large ion radius of dopant correlates with superconductivity.

Hole-like charge carriers dominate at low temperatures.

Abstract

Superconductivity at about 15.6 K was achieved in Tb_{1-x}Ca_xFeAsO by partially substituting Tb^{3+} with Ca^{2+} in the nominal doping region x = 0.40 \sim 0.50. A detailed investigation was carried out in a typical sample with doping level of x = 0.44. The upper critical field of this sample was estimated to be 77 Tesla from the magnetic field dependent resistivity data. The domination of hole-like charge carriers in the low-temperature region was confirmed by Hall effect measurements. The comparison between the calcium-doped sample Pr_{1-x}Ca_xFeAsO (non-superconductive) and the Strontium-doped sample Pr_{1-x}Sr_xFeAsO (superconductive) suggests that a lager ion radius of the doped alkaline-earth element compared with that of the rare-earth element may be a necessary requirement for achieving superconductivity in the hole-doped 1111 phase.