title: Nematic quantum critical point without magnetism in FeSe1-xSx superconductors.
abstract: In most unconventional superconductors, the importance of antiferromagnetic 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 electron pairing. In these materials, however, such nematic correlations are intertwined with antiferromagnetic or charge orders, preventing the identification of the essential role of nematic fluctuations. This calls for new materials having only nematicity without competing or coexisting orders. Here we report systematic elastoresistance measurements in FeSe1-xSx superconductors, which, unlike other iron-based families, exhibit an electronic nematic order without accompanying antiferromagnetic order. We find that the nematic transition temperature decreases with sulfur content x; whereas, the nematic fluctuations are strongly enhanced. Near [Formula: see text], the nematic susceptibility diverges toward absolute zero, revealing a nematic quantum critical point. The obtained phase diagram for the nematic and superconducting states highlights FeSe1-xSx as a unique nonmagnetic system suitable for studying the impact of nematicity on superconductivity.
authors.affiliation: Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan;
authors.forename: Suguru
authors.initials: S
authors.lastname: Hosoi
authors.affiliation: Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan;
authors.forename: Kohei
authors.initials: K
authors.lastname: Matsuura
authors.affiliation: Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan;
authors.forename: Kousuke
authors.initials: K
authors.lastname: Ishida
authors.affiliation: Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan;
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan;
authors.forename: Yuta
authors.initials: Y
authors.lastname: Mizukami
authors.affiliation: Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Watashige
authors.affiliation: Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Kasahara
authors.affiliation: Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Matsuda
authors.affiliation: Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan; shibauchi@k.u-tokyo.ac.jp.
authors.forename: Takasada
authors.initials: T
authors.lastname: Shibauchi
keywords: electronic nematicity; iron-based superconductors; nematic susceptibility; quantum critical point; unconventional superconductivity