Superconductivity in single-layer films of FeSe with a transition temperature above 100 K

Recently, interface has been employed to enhance superconductivity in the single-layer FeSe films grown on SrTiO3(001)(STO) with a possible Tc of ~ 80 K, which is nearly ten times of the Tc of bulk FeSe and is above the Tc record of 56 K for the bulk Fe-based superconductors. This work together with those on superconducting oxides interfaces revives the long-standing idea that electron pairing at a two-dimensional (2D) interface between two different materials is a potential path to high transition temperature (Tc) superconductivity. Subsequent angle-resolved photoemission spectroscopy (ARPES) measurements revealed different electronic structure from those of bulk FeSe with a superconducting-like energy gap closing at around 65K. However, previous ex situ electrical transport measurements could only detect the zero-resistance below ~30 K. Here we report the observation of high Tc superconductivity in the FeSe/STO system. By in situ 4-point probe (4PP) electrical transport measurement that can be conducted at an arbitrary position of the FeSe film on STO, we detected superconductivity above 100 K. Our finding makes FeSe/STO the exciting and ideal research platform for higher Tc superconductivity.