Enhancement of superconductivity in FeSe1−xTexby Li doping

The study investigated the chemical doping effect of Li in the Fe(Se,Te) system. With the addition of Li, the NiAs phase was precipitated, which resulted in worse superconductivity in FeSe samples. The XRD results indicated that chemical stress was found in the FeTe system which showed no superconductivity by doping Li. However, it was noticeable that the Tc was increased (1–1.5 K) and the enhancement of diamagnetic force was found in FeSe1−xTex (x = 0.5–1) with 1 wt% Li doping. The lattice constant of the c-axis increased with increasing content of Li, implying that the Li interstitial sites are along the c-axis. Furthermore, the XRD results showed that the enhanced superconductivity of FeSe1−xTex resulted from the large stress fields in FeSe1−xTex. The stress field effect was retarded by the large quantity of Li additives.