Emergent Superconductivity in FeTe Single Crystals

Iron telluride (FeTe) has long been regarded as an antiferromagnetic (AFM) metal sans superconductivity. Our recent studies on molecular beam epitaxy (MBE)-grown FeTe films reveal that excess interstitial Fe in FeTe obscures its intrinsic electronic properties. In this work, we demonstrate controlled removal of interstitial Fe from FeTe single crystals via tellurium-flux annealing in an MBE chamber. In situ spin-polarized scanning tunneling microscopy (SP-STM) measurements reveal local suppression of the native AFM order at domain boundaries. Complementary scanning tunneling spectroscopy (STS) measurements show distinct local density of states features between AFM and nonmagnetic regions, with a superconducting gap of ~3.4 meV observed in the nonmagnetic regions. Furthermore, quasiparticle interference (QPI) mapping in AFM regions uncovers spin-dependent electronic reconstruction, providing microscopic insight into the magnetic order. Our results establish a clean and tunable platform to probe the interplay between magnetism and superconductivity, thereby paving the way towards realizing superconductivity in FeTe single crystals.