High-temperature superconductivity and its robustness against magnetic polarization in monolayer FeSe on EuTiO3
Chong Liu, Hyungki Shin, Andrin Doll, Hsiang‐Hsi Kung, Ryan Day, B. A. Davidson, Jan Dreiser, G. Levy, A. Damascelli, Cínthia Piamonteze, Ke Zou
Abstract
Abstract Spin degree of freedom generally plays an important role in unconventional superconductivity. In many of the iron-based compounds, superconductivity is found in close proximity to long-range antiferromagnetic order, whereas monolayer FeSe grown on SrTiO 3 , with enhanced superconductivity, exhibits no magnetic or nematic ordering. Here we grow monolayer and multilayer FeSe on antiferromagnetic EuTiO 3 (001) layers, in an effort to introduce a spin polarization in proximity to the superconductivity of FeSe. By X-ray magnetic dichroism, we observe an antiferromagnet–ferromagnet switching on Eu and Ti sites in EuTiO 3 driven by the applied magnetic field, with no concomitant spin polarization on the Fe site of FeSe. Transport measurements show enhanced superconductivity of monolayer FeSe on EuTiO 3 with a transition temperature of ~30 K. The band structure revealed by photoemission spectroscopy is analogous to that of FeSe/SrTiO 3 . Our work creates a platform for the interplay of spin and unconventional superconductivity in the two-dimensional limit.