Anomalous high-magnetic field electronic state of the nematic superconductors FeSe₁₋ₓSₓ

Understanding superconductivity requires detailed knowledge of the normal electronic state from which it emerges. A nematic electronic state that breaks the rotational symmetry of the lattice can potentially promote unique scattering relevant for superconductivity. Here, we investigate the normal transport of superconducting FeSe1−xSx across a nematic phase transition using high-magnetic fields up to 69 T to establish the temperature and field dependencies. We find that the nematic state is dominated by a linear resistivity at low temperatures that evolves towards Fermi-liquid behavior, depending on the composition x and the impurity level. Near the nematic end point, we find an extended temperature regime with ∼T1.5 resistivity, different from the behavior found near an antiferromagnetic critical point. The variation of the resistivity exponent with temperature reflects the importance of the nematoelastic coupling that can also suppress divergent critical fluctuations at the nematic end point. The transverse magnetoresistance inside the nematic phase has a ∼H1.55 dependence over a large magnetic field range and it displays an unusual peak at low temperatures inside the nematic phase. ... mehrOur study reveals anomalous transport inside the nematic phase, influenced by both changes in the electronic structure and the scattering with the lattice and spin fluctuations.