Electronic evidence of an insulator–superconductor crossover in single-layer FeSe/SrTiO3films

Junfeng He, Xu Liu, Wenhao Zhang, Lin Zhao, Defa Liu, Shaolong He, Daixiang Mou, Fangsen Li, Chenjia Tang, Zhi Li, Lili Wang, Yingying Peng (+12 others)
2014 Proceedings of the National Academy of Sciences of the United States of America  
In high temperature cuprate superconductors, it is now generally agreed that the parent compound is a Mott insulator and superconductivity is realized by doping the antiferromagnetic Mott insulator. In the iron-based superconductors, however, the parent compound is mostly antiferromagnetic metal, raising a debate on whether an appropriate starting point should go with an itinerant picture or a localized picture. It has been proposed theoretically that the parent compound of the iron-based
more » ... onductors may be on the verge of a Mott insulator, but so far no clear experimental evidence of doping-induced Mott transition has been available. Here we report an electronic evidence of an insulator-superconductor transition observed in the single-layer FeSe films grown on the SrTiO3 substrate. By taking angle-resolved photoemission measurements on the electronic structure and energy gap, we have identified a clear evolution of an insulator to a superconductor with the increasing doping. This observation represents the first example of an insulator-superconductor transition via doping observed in the iron-based superconductors. It indicates that the parent compound of the iron-based superconductors is in proximity of a Mott insulator and strong electron correlation should be considered in describing the iron-based superconductors.
doi:10.1073/pnas.1414094112 pmid:25502774 pmcid:PMC4284572 fatcat:b6gpl4jmqbeltanrwe2kke4rr4