Magnetic-Field-Induced Spin Nematicity in FeSe1 – x S x and FeSe1 – y Te y Superconductor SystemsSupported by the National Key Research and Development Program of China (Grant Nos. 2016YFA0300300 and 2017YFA0303003), the National Natural Science Foundation of China (Grant Nos. 12061131005, 11834016, and 11888101), the Strategic Priority Research Program of Chinese Academy of Sciences (Grant Nos. XDB25000000), and the

Abstract

The angular-dependent magnetoresistance (AMR) of the ab plane is measured on the single crystals of iron-chalcogenide FeSe1–x S x (x = 0, 0.07, 0.13 and 1) and FeSe1–y Te y (y = 0.06, 0.61 and 1) at various temperatures under fields up to 9 T. A pronounced twofold-anisotropic carrier-scattering effect is identified by AMR, and attributed to a magnetic-field-induced spin nematicity that emerges from the tetragonal normal-state regime below a characteristic temperature T sn. This magnetically polarized spin nematicity is found to be ubiquitous in the isoelectronic FeSe1–x S x and FeSe1–y Te y systems, no matter whether the sample shows an electronic nematic order at T s ≲ T sn, or an antiferromagnetic order at T N < T sn, or neither order. Importantly, we find that the induced spin nematicity shows a very different response to sulfur substitution from the spontaneous electronic nematicity: The spin-nematic T sn is not suppressed but even enhanced by the substitution, whereas the electronic-nematic T s is rapidly suppressed, in the FeSe1–x S x system. Furthermore, we find that the superconductivity is significantly suppressed with the enhancement of the induced spin nematicity in both FeSe1–x S x and FeSe1–y Te y samples.