Drastic field-induced resistivity upturns as signatures of unconventional magnetism in superconducting iron chalcogenides

TL;DR

This study investigates how high magnetic fields and pressure influence electronic and magnetic phases in FeSe$_{0.96}$S$_{0.04}$, revealing field-induced resistivity upturns as signatures of unconventional magnetism intertwined with superconductivity.

Contribution

It provides detailed insights into the pressure and magnetic field dependence of electronic and magnetic phases in FeSe$_{0.96}$S$_{0.04}$, highlighting the role of magnetic fields in stabilizing complex electronic states.

Findings

Resistivity upturns indicate spin-density wave phase within the nematic phase.

High magnetic fields induce significant resistivity upturns reflecting field-induced order.

Superconductivity and magnetic anomalies are enhanced together under high magnetic fields.

Abstract

Electronic scattering is a powerful tool to identify underlying changes in electronic behavior and incipient electronic and magnetic orders. The nematic and magnetic phases are strongly intertwined under applied pressure in FeSe, however, the additional isoelectronic substitution of sulphur offers an elegant way to separate them. Here we report the detailed evolution of the electronic and superconducting behaviour of FeSe$_{0.96}$S$_{0.04}$ under applied pressure via longitudinal magnetoresistance studies up to 15T. At intermediate pressures, inside the nematic phase, the resistivity displays an upturn in zero magnetic field, which is significantly enhanced in the magnetic field, suggesting the stabilization of a spin-density wave phase, which competes with superconductivity. At higher pressures, beyond the nematic phase boundaries, the resistivity no longer displays any clear anomalies in the zero magnetic field, but an external magnetic field induces significant upturns in resistivity reflecting a field-induced order, where superconductivity and magnetic anomalies are enhanced in tandem. This study highlights the essential role of high magnetic fields in stabilizing different electronic phases and revealing a complex interplay between magnetism and superconductivity tuned by applied pressure in FeSe$_{1-x}$S$_{x}$.