Pressure effects on superconducting properties of single-crystalline Co doped NaFeAs

TL;DR

This study investigates how external pressure influences the superconducting properties of single-crystalline NaFe1-xCoxAs, revealing maximum Tc enhancement up to 31 K and highlighting differences in electronic structure between doping levels.

Contribution

It provides new insights into pressure effects on superconductivity in NaFe1-xCoxAs and compares these effects with other iron-based superconductors, emphasizing the role of electronic structure.

Findings

Maximum Tc reaches 31 K under pressure.

Positive pressure coefficient enhances Tc in various doping levels.

Superconductivity cannot be induced by pressure in heavily overdoped samples.

Abstract

Resistivity and magnetic susceptibility measurements under external pressure were performed on single-crystals NaFe1-xCoxAs (x=0, 0.01, 0.028, 0.075, 0.109). The maximum Tc enhanced by pressure in both underdoped and optimally doped NaFe1-xCoxAs is the same, as high as 31 K. The overdoped sample with x = 0.075 also shows a positive pressure effect on Tc, and an enhancement of Tc by 13 K is achieved under pressure of 2.3 GPa. All the superconducting samples show large positive pressure coefficient on superconductivity, being different from Ba(Fe1-xCox)2As2. However, the superconductivity cannot be induced by pressure in heavily overdoped non-superconducting NaFe0.891Co0.109As. These results provide evidence for that the electronic structure is much different between superconducting and heavily overdoped non-superconducting NaFe1-xCoxAs, being consistent with the observation by angle-resolved photoemission spectroscopy.