Se and Te Doping Study of the FeSe Superconductors

Abstract

Here we present a systematic study of correlation between superconductivity with Se-content and Te-doping to the -FeSe system. Detailed structural and specific heat measurements at low temperature suggest that the occurrence of superconductivity is closely related to the presence of P-1 (triclinic) symmetry at low temperature. Magnetic field dependence of the resistive transition in polycrystalline -FeSe 1-x and FeSe 1-x Te x suggest that Te-doping tends to induce the system to become more 2D-like and enhances substantially the upper critical field value, whereas the FeSe system behaves more like 3D superconductor.