High pressure study on LaFeAsO with different Tc

TL;DR

This study investigates how applying high pressure affects the superconducting transition temperature of LaFeAsO and its fluorine-doped variants, revealing a maximum Tc at certain pressures and insights into the underlying electronic mechanisms.

Contribution

It provides the first detailed pressure dependence of Tc in LaFeAsO and its doped forms, highlighting the role of orbital degeneracy and electron density in superconductivity enhancement.

Findings

Tc increases with pressure initially, then decreases after reaching a maximum.

The highest Tc recorded is ~50 K at 1.5 GPa for LaFeAsO.

Pressure-induced changes are linked to electronic structure modifications.

Abstract

We report studies on pressure dependence of superconducting transition temperature (Tc) of LaFeAsO, LaFeAs(O0.5F0.5) and LaFeAs(O0.89F0.11) samples. In-situ resistance measurements under high pressure showed that the Tc of these three compounds increases with pressure initially, reaches a maximum value and then decreases with further increasing pressure, although the Tc at ambient pressure are different. The onset Tc of LaFeAsO is ~50 K at 1.5 GPa, which is the highest record in La-based oxypnicited system. The significant change in Tc induced by pressure is attributed to the orbital degeneracy and the electron density of state at the Fermi level.