Dome-shaped magnetic order competing with high-temperature superconductivity at high pressures in FeSe

TL;DR

This study reveals a hidden magnetic dome in FeSe under high pressure that competes with superconductivity, providing insights into the complex interplay of electronic orders and high-temperature superconductivity.

Contribution

It uncovers a pressure-induced magnetic dome in FeSe that coexists and competes with superconductivity, advancing understanding of electronic orders in iron-based superconductors.

Findings

Magnetic order is suppressed as superconductivity is enhanced above 6 GPa.

Anomalous transport suggests pseudogap formation in high-pressure phases.

Resistivity behavior resembles that of high-${T_{ m c}}$ cuprates.

Abstract

The coexistence and competition between superconductivity and electronic orders, such as spin or charge density waves, have been a central issue in high transition-temperature (${T_{\rm c}}$) superconductors. Unlike other iron-based superconductors, FeSe exhibits nematic ordering without magnetism whose relationship with its superconductivity remains unclear. More importantly, a pressure-induced fourfold increase of ${T_{\rm c}}$ has been reported, which poses a profound mystery. Here we report high-pressure magnetotransport measurements in FeSe up to $\sim9$ GPa, which uncover a hidden magnetic dome superseding the nematic order. Above ${\sim6}$ GPa the sudden enhancement of superconductivity (${T_{\rm c}\le38.3}$ K) accompanies a suppression of magnetic order, demonstrating their competing nature with very similar energy scales. Above the magnetic dome we find anomalous transport properties suggesting a possible pseudogap formation, whereas linear-in-temperature resistivity is observed above the high-${T_{\rm c}}$ phase. The obtained phase diagram highlights unique features among iron-based superconductors, but bears some resemblance to that of high-${T_{\rm c}}$ cuprates.