  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.
