Presenter: Prof. Dong Qian (上海交通大学)
Topic: Magnetic order in single monolayer FeSe/SrTiO3(001) films
Location: Conference Room G, BLDG 909
Single monolayer (ML) FeSe film grown on Nd-doped SrTiO3(001) substrate shows the highest superconducting transition temperature (TC ~ 100 K) among the iron-based superconductors (iron-pnictide), while the TC of bulk FeSe is only ~ 8 K. AFM spin fluctuation was proposed to be crucial in iron-pnictide. Based on spin fluctuation scenario, several proposals have been raised to understand the FeSe/SrTiO3 system. Though bulk FeSe does not show AFM order, calculations proposed that the parent FeSe/SrTiO3 film is AFM and AFM interaction is enhanced in the interface. Experimentally, lacking of directly probe, the magnetic state of FeSe/SrTiO3 films remains mysterious. In this talk, I will present the direct evidences that the parent 1-ML FeSe/SrTiO3 film is AFM. We find that AFM interaction is strongly enhanced in 1-ML FeSe/SrTiO3 film compared with the “isolated” 1-ML film. AFM order disappears and superconductivity appears by electron doping. Our findings provide crucial information to understand the superconducting behavior in FeSe/SrTiO3 films.