High Pressure Studies on Fe-Pnictide Superconductors

TL;DR

This review discusses how applying high pressure influences magnetic and superconducting properties of various Fe-pnictide compounds, revealing pressure-induced superconductivity and changes in transition temperatures.

Contribution

It provides a comprehensive overview of pressure effects on Fe-pnictide superconductors, highlighting the role of chemical and physical pressure in tuning superconductivity.

Findings

Pressure decreases magnetic transition temperatures in undoped compounds.

Superconducting Tc increases under pressure in underdoped FeAs-pnictides.

Undoped FeSe exhibits the largest pressure coefficient of Tc.

Abstract

A review of high-pressure studies on Fe-pnictide superconductors is given. The pressure effects on the magnetic and superconducting transitions are discussed for different classes of doped and undoped FeAs-compounds, ROFeAs (R = rare earth), AeFe2As2 (Ae = Ca, Sr, Ba), and AFeAs (A = Li, Na). Pressure tends to decrease the magnetic transition temperature in the undoped or only slightly doped compounds. The superconducting Tc increases with pressure for underdoped FeAs-pnictides, remains approximately constant for optimal doping, and decreases linearly in the overdoped range. The undoped LaOFeAs and AeFe2As2 become superconducting under pressure although nonhydrostatic pressure conditions seem to play a role in CaFe2As2. The superconductivity in the (undoped) AFeAs is explained as a chemical pressure effect due to the volume contraction caused by the small ionic size of the A-elements. The binary FeSe shows the largest pressure coefficient of Tc in the Se-deficient superconducting phase.