Large anisotropic uniaxial pressure dependencies of Tc in single crystalline Ba(Fe0.92Co0.08)2As2

TL;DR

This study reveals highly anisotropic uniaxial pressure effects on the critical temperature in Ba(Fe0.92Co0.08)2As2, showing strong coupling between lattice parameters and superconductivity, with implications for layered superconductor behavior.

Contribution

The paper provides the first detailed measurement of uniaxial pressure dependencies of Tc in this compound using high-resolution dilatometry and Ehrenfest relation analysis.

Findings

Uniaxial pressure along the a-axis increases Tc significantly.

Uniaxial pressure along the c-axis decreases Tc.

Strong coupling between c/a ratio and superconducting order.

Abstract

Using high-resolution dilatometry, we study the thermodynamic response of the lattice parameters to superconducting order in a self-flux grown Ba(Fe0.92Co0.08)2As2 single crystal. The uniaxial pressure dependencies of the critical temperature of Tc, calculated using our thermal expansion and specific heat data via the Ehrenfest relation, are found to be quite large and very anisotropic (dTc/dpa = 3.1(1) K/GPa and dTc/dpc = - 7.0(2) K/GPa). Our results show that there is a strong coupling of the c/a ratio to superconducting order, which demonstrates that Tc is far from the optimal value. A surprising similarity with the uniaxial pressure effects in several other layered superconductors is discussed.