Tuning nematic electronic phases, electronic correlations and shifting the dxy hole band via isoelectronic substitution in FeSe_1-xS_x and FeSe_1-xTe_x

Electronic nematic phase of iron-chalcogenides superconductors can be finely tuned via isoelectronic substitution and their electronic behaviour can be explored in detail via angle-dependent photoemission spectroscopy and quantum oscillations [1,2]. In this talk, I will compare angle-resolved photoemission studies probing the nematic electronic phase of FeSe1-xSx versus FeSe_1-xTe_x [3,4,5]. I will discuss the evolution of the electronic bands, the quasiparticle effective masses as well as the sensitivity of the d_xy hole band to the chalcogen height. We find that the dxy hole band shifts significantly with increasing the chalcogen height and it could be involved in promoting an additional pairing channel and enhance the density of states to stabilize the second superconducting dome in FeSe_1−xTe_x systems [5]. This is in contrast to FeSe_1-xS_x series, where the d_xy band does not shift and there is no enhancement in superconductivity outside the nematic phase, despite both series displaying large nematic susceptibility at the nematic end point.