Robust T c in element molybdenum up to 160 GPa

Abstract

Element superconductors with the single atoms provide clean and fundamental platforms for studying superconductivity. Although elements with d electrons are usually not favored by conventional BCS, the record superconducting critical temperature (T c) in element scandium (Sc) has further ignited the intensive attention on transition metals. The element molybdenum (Mo) with a half-full d-orbital is studied in our work, which fills the gap in the study of Mo under high pressure and investigates the pressure dependence of superconductivity. In this work, we exhibit a robust superconductivity of Mo in the pressure range of 5 GPa to 160 GPa via high-pressure electrical transport measurements, the T c varies at a rate of 0.013 K/GPa to 8.56 K at 160 GPa. Moreover, the superconductivity is evidenced by the T c shifting to lower temperature under applied magnetic fields, and the upper critical magnetic fields are extrapolated by the WHH equation and GL equation; the results indicate that the maximum upper critical magnetic field is estimated to be 8.24 T at 137 GPa. We further investigate the superconducting mechanism of Mo, the theoretical calculations indicate that the superconductivity can be attributed to the strong coupling between the electrons from the partially filled d band and the phonons from the frequency zone of 200–400 cm−1.