Superconductivity at 9K in Mo5PB2 with evidence for multiple gaps

TL;DR

This study reports superconductivity near 9K in Mo5PB2, supported by experimental measurements and electronic structure calculations, indicating possible multiple gaps and phonon-mediated pairing.

Contribution

First demonstration of superconductivity in Mo5PB2 with detailed experimental and theoretical analysis revealing multiple gaps and intermediate coupling.

Findings

Superconductivity at 9.2 K in Mo5PB2.

Evidence for multiple superconducting gaps.

Estimated upper critical field of about 17 kOe.

Abstract

Superconductivity is observed with critical temperatures near 9K in the tetragonal compound Mo5PB2. This material adopts the Cr5B3 structure type common to supercondcuting Nb5Si3-xBx, Mo5SiB2, and W5SiB2, which have critical temperatures of 5.8-7.8 K. We have synthesized polycrystalline samples of the compound, made measurements of electrical resistivity, magnetic susceptibility, and heat capacity, and performed first principles electronic structure calculations. The highest Tc value (9.2 K) occurs in slightly phosphorus rich samples, with composition near Mo5P1.1B1.9, and the upper critical field Hc2 at T = 0 is estimated to be about 17 kOe. Together, the measurements and band structure calculations indicate intermediate coupling (lambda = 1.0), phonon mediated superconductivity. The temperature dependence of the heat capacity and upper critical field Hc2 below Tc suggest multiple superconducting gaps may be present.