The effect of impurity scattering on the electronic and superconducting properties of FeSe via Cu-substitution tuned by applied pressure.*

An important aspect in understanding the superconducting pair mechanism and the scattering affecting normal electronic properties in iron-based superconductors is via controlled disorder. The substitution of Cu can give rise to intriguing electronic properties compared with other transition metals, like Co and Ni, that often helps to stabilize a high-Tc superconducting state. We present a detailed study on the role of doping and disorder on the superconducting and electronic properties of Cu-FeSe. The nematic and superconducting phases are both quickly suppressed with copper substitution and the carrier mobilities decrease significantly. In addition, studies using applied hydrostatic pressure revealed the suppression of the nematic phase, whilst the superconductivity reaches 22K at 20kbar in a regime where a magnetic phase is stabilized. The pressure-temperature phase diagram reveals that the magnetic phase is highly sensitive to disorder, whereas the superconducting phase remains rather robust.