Interface superconductivity in FeSe thin films on SrTiO₃ grown by the PLD technique

Iron chalcogenide superconductor, FeSe, has attracted much attention because monolayer films on SrTiO₃ (STO) grown by molecular beam epitaxy (MBE) exhibit interface superconductivity with significantly enhanced superconducting transition temperature (T_c) from 9 K to 40-65 K. Further T_c enhancement is expected to be achieved through fabricating various heterostructures with other oxide materials. In this context, Pulsed laser deposition (PLD) is a promising growth technique rather than MBE.

Here, we report the successful realization of interface superconductivity in FeSe/STO using PLD. We found that using atomically flat STO substrates is crucial in realizing interface superconductivity in FeSe/STO by PLD. All films showed superconductivity with onset T_c much higher than that of bulk FeSe, which cannot be explained by the strain effects of the same material established so far. Furthermore, the grown films showed large anisotropy of the upper critical fields with H_c2^H//ab/H_c2^H//c larger than 11. These values are higher than those of intercalated FeSe compounds which show large anisotropy induced by the expansion of distance between FeSe layers. These results indicate that superconductivity in the PLD-grown FeSe/STO is confined at the interface between FeSe and STO.