Abstract
The tetragonal Mo5PB2 compound was recently reported to show superconductivity with a critical temperature up to 9.2 K. In search of evidence for multiple superconducting gaps in Mo5PB2, comprehensive measurements, including magnetic susceptibility, electrical resistivity, heat capacity, and muon-spin rotation and relaxation measurements were carried out. Data from both low-temperature superfluid density and electronic specific heat suggest a nodeless superconducting ground state in Mo5PB2. Two superconducting energy gaps Δ0 = 1.02 meV (25%) and 1.49 meV (75%) are required to describe the low-T electronic specific-heat data. The multigap features are clearly evidenced by the field dependence of the electronic specific-heat coefficient and the Gaussian relaxation rate in the superconducting state (i.e., superfluid density), as well as by the temperature dependence of the upper critical field. By combining our extensive experimental results with numerical band-structure calculations, we provide compelling evidence of multigap superconductivity in Mo5PB2.
Highlights
The T5M3 family, where T is a transition or rare-earth metal and M a-transition metal or a metalloid element, features three distinct structural symmetries: orthorhombic Yb5Sb3-type (Pnma, no. 62), tetragonal Cr5B3-type (I4/mcm, no. 140), and hexagonal Mn5Si3-type (P63/mcm, no. 193)
Its multigap features are strongly evidenced by the field-dependent electronic specific-heat coefficient, as well as by the superconducting μSR relaxation, the latter being highly consistent with the temperature dependence of the upper critical field
Crystal structure and phase purity The crystal structure and the purity of Mo5PB2 polycrystalline samples were checked via powder x-ray powder diffraction (XRD) at room temperature
Summary
The T5M3 family, where T is a transition or rare-earth metal and M a (post)-transition metal or a metalloid element, features three distinct structural symmetries: orthorhombic Yb5Sb3-type (Pnma, no. 62), tetragonal Cr5B3-type (I4/mcm, no. 140), and hexagonal Mn5Si3-type (P63/mcm, no. 193). On the other hand, when T is occupied by other 3d metals, such as Mn or Fe, both T5SiB2 and T5PB2 are ferromagnets with high Curie temperatures Currently they are being considered for room-temperature magnetocaloric applications or as rare-earth-free permanent magnets [2,3,4,5]. A new member of the Cr5B3-type series, namely Mo5PB2, was synthesized and shown to exhibit superconductivity (SC) with a critical temperature Tc = 9.2 K [11], the highest Tc recorded in this family of compounds. Its multigap features are strongly evidenced by the field-dependent electronic specific-heat coefficient, as well as by the superconducting μSR relaxation, the latter being highly consistent with the temperature dependence of the upper critical field
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