Electronic State-Regulated Magnetic Phenomena in Single-Crystal FeSe

In contrast to the observed high-temperature superconductivity in monolayer FeSe/SrTiO3 films, akin to CoSb/SrTiO3, the bulk counterpart, FeSe, does not exhibit superconductivity even under elevated pressure, and its magnetic characteristics remain subject to debate. This investigation delves into the electrical and magnetic attributes, alongside X-ray photoelectron spectroscopy (XPS) analysis, of FeSe mono-crystal. Magnetic and electrical transport assessments indicate that FeSe demonstrates characteristics of a Pauli paramagnetic metal within non-Fermi liquid traits. XPS analysis further reveals that the Fe and Se pair in FeSe exist in a zero-valence state, forming a predominantly metallic-bonded alloy. The Pauli paramagnetism observed in FeSe is ascribed to its itinerant electrons. The comprehension of the electronic states in FeSe mono-crystal not only clarifies its lack of magnetic characteristics but also paves the way for exploring potential high-temperature superconductivity.