Physics

Photoemission spectroscopy

Angle-resolved photoemission spectroscopy

Pairing

X-ray photoelectron spectroscopy

Materials science

Condensed matter physics

Superconducting transition temperature

Nuclear magnetic resonance

Superconductivity

Quantum mechanics

Electrical resistivity and conductivity

Doping

Electronic structure

Nature Materials

Monolayer iron selenide grown on SrTiO3 has recently gained attention due to suggestive evidence it superconducts at high temperature. In situ electrical transport measurements now reveal a transition temperature above 100 K. Recent experiments on FeSe films grown on SrTiO3 (STO) suggest that interface effects can be used as a means to reach superconducting critical temperatures (Tc) of up to 80 K (ref.&nbsp;1). This is nearly ten times the Tc of bulk FeSe and higher than the record value of 56 K for known bulk Fe-based superconductors2. Together with recent studies of superconductivity at oxide heterostructure interfaces3,4,5,6, these results rekindle the long-standing idea that electron pairing at interfaces between two different materials can be tailored to achieve high-temperature superconductivity7,8,9,10,11,12. Subsequent angle-resolved photoemission spectroscopy measurements of the FeSe/STO system revealed an electronic structure distinct from bulk FeSe (refs&nbsp;13, 14), with an energy gap vanishing at around 65 K. However, ex situ electrical transport measurements1,15 have so far detected zero resistance—the key experimental signature of superconductivity—only below 30 K. Here, we report the observation of superconductivity with Tc above 100 K in the FeSe/STO system by means of in situ four-point probe electrical transport measurements. This finding confirms FeSe/STO as an ideal material for studying high-Tc superconductivity.

Superconductivity above 100 K in single-layer FeSe films on doped SrTiO3