Nematic quantum critical point without magnetism in FeSe1−xSx superconductors

In most unconventional superconductors, the importance of antifer- romagnetic fluctuations is widely acknowledged. In addition, cuprate and iron-pnictide high-temperature superconductors often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, whose fluctuations may also play a key role for elec- tron pairing. In these materials, however, such nematic correlations are intertwined with antiferromagnetic or charge orders, preventing us to identify the essential role of nematic fluctuations. This calls for new materials having only nematicity without competing or co- existing orders. Here we report systematic elastoresistance mea- surements in FeSe1−xSx superconductors, which, unlike other iron- based families, exhibit an electronic nematic order without accom- panying antiferromagnetic order. We find that the nematic transition temperature decreases with sulfur content x, whereas the nematic fluctuations are strongly enhanced. Near x 0.17, the nematic sus- ceptibility diverges towards absolute zero, revealing a nematic quan- tum critical point. The obtained phase diagram for the nematic and superconducting states highlights FeSe1−xSx as a unique nonmag- netic system suitable for studying the impact of nematicity on super- conductivity.UTokyo Research掲載「新しい種類の超伝導の発生源になりうるか？」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/discovery-may-point-to-new-source-of-superconductivity.htmlUTokyo Research "Discovery may point to new source of superconductivity" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/discovery-may-point-to-new-source-of-superconductivity.htm