  Dome-shape superconductivity phase diagram can commonly be observed in
cuprate and iron-based systems via tuning parameters such as charge carrier
doping, pressure, bond angle, and etc. We report doping electrons from
transition-metal elements (TM = Co, Ni) substitution can induce high-Tc
superconductivity around 35 K in Ca0.94La0.06Fe2As2, which emerges abruptly
before the total suppression of the innate
spin-density-wave/anti-ferromagnetism (SDW/AFM) state. Unexpectedly, the onset
critical temperature for the high-Tc superconductivity stays constant for a
wide range of TM doping. Possible extrinsic factors like phase separation,
chemical inhomogeneity, and charge carrier cancelation effect are all excluded.
This anomalous charge carrier density independent SC is very similar to the
interface superconductivity in La2-xSrxCuO4-La2CuO4 bilayer system. The further
verified two-dimensional (2D) nature of superconductivity by the Tinkham's
angular-dependent critical field model as well as by the angle-resolved
magneto-resistance measurements jointly supports the idea of interfacial effect
induced high-Tc superconductivity.

Superconductivity