Extended strange metal regime in a pure nematic quantum critical superconductor

Abstract

High-temperature superconductivity often emerges from a strange metallic state, where the electrical resistivity exhibits a linear-in-temperature dependence over an anomalously extended temperature range. The prevailing belief is that magnetic critical fluctuations gives rise to strange metallicity, enhancing the superconducting transition temperature. Here, using high pulsed magnetic fields, we have uncovered the strange metallic ground state hidden below the superconducting dome of nonmagnetic FeSe$_{1-x}$Te$_{x}$, which harbors a quantum critical point (QCP) of pure electronic nematicity, characterized by spontaneous rotational symmetry breaking. Unlike the conventional quantum criticality, this strange metallic state does not appear in a fan-shaped region above the singular QCP but spans a wide compositional range, where pairing interactions are strengthened by nonmagnetic nematic critical fluctuations. This stands in sharp contrast to the much cleaner system FeSe$_{1-x}$S$_{x}$, which displays a quantum critical fan above nematic QCP, indicating that disorder-induced spatial randomness of the nematic fluctuations likely enlarges the QCP of FeSe$_{1-x}$Te$_{x}$ into an extended region of criticality, as suggested by relevant hybrid Quantum Monte Carlo simulations. These observations highlight superconductivity promoted by a unique interplay between pure nematic critical fluctuations, strange metallicity and disorder, providing new insight into the emergence of non-Fermi-liquid transport in various correlated materials.