Thermal expansion and Gr\"uneisen parameters of Ba(Fe1-xCox)2As2 - a thermodynamic quest for quantum criticality

TL;DR

This study uses thermal expansion measurements to explore the pressure dependence of entropy and quantum criticality in Ba(Fe1-xCox)2As2, revealing features consistent with a pressure-tuned quantum critical point and linking magnetic and superconducting phases.

Contribution

It demonstrates that uniaxial pressure acts as an effective tuning parameter and uncovers thermodynamic signatures of quantum criticality in the material.

Findings

Uniaxial pressure correlates with doping levels.

Features indicative of a pressure-tuned quantum critical point are observed.

Electronic and magnetic Grüneisen parameters link magnetic and superconducting transitions.

Abstract

Thermal expansion data are used to study the uniaxial pressure dependence of the electronic/magnetic entropy of Ba(Fe1-xCox)2As2. Uniaxial pressure is found to be proportional to doping and, thus, also an appropriate tuning parameter in this system. Many of the features predicted to occur for a pressure-tuned quantum critical system, in which superconductivity is an emergent phase hiding the critical point, are observed. The electronic/magnetic Gr\"uneisen parameters associated with the spin-density wave and superconducting transitions further demonstrate an intimate connection between both ordering phenomena.