Superconductivity at 9 K inMo5PB2with evidence for multiple gaps

Abstract

Superconductivity is observed with critical temperatures near 9 K 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 ≈ 17 kOe. Together, the measurements and band structure calculations indicate intermediate coupling (λ = 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.

Chemical order or disorder – a theoretical stability expose for expanding the compositional space of quaternary metal borides

“…22,29 T2 phases have an M 5 AB 2 composition in an I4/mcm space group symmetry, where M is a transition metal from Groups 5 to 9, and A is an Aelement (Si, Ge, and P). T2 phases are attractive due to their high oxidation resistance, 30 nearly isotropic thermal expansion, 31 superconducting properties 32,33 and potential for use as rare-earth free permanent magnets. [34][35][36] We have recently shown that metal alloying in Si-based T2 phases holds potential for a range of new compositions, including the discovered out-of-plane ordered Ti 4 MoSiB 2 , called o-MAB.…”

A comprehensive DFT based insights into the physical properties of tetragonal superconducting Mo5PB2

“…One of the interesting subsets of these compounds is the ternary borides with stoichiometries M 5 XB 2 (where X = P, Si). These systems exhibit many interesting electronic ground states [2]. It has been reported that these ternary borides are formed with many transition metals including the 3d transition metals from V to Co, the 4d transition metals Nb and Mo, and the 5d transition metal W [2].…”

“…These systems exhibit many interesting electronic ground states [2]. It has been reported that these ternary borides are formed with many transition metals including the 3d transition metals from V to Co, the 4d transition metals Nb and Mo, and the 5d transition metal W [2]. For instance, Mn 5 SiB 2 shows ferromagnetic behavior with Curie temperature at room temperature [3].…”

“…Few years back, a new compound, namely Mo 5 PB 2 , was added to the series of the tetragonal Cr 5 B 3 -type. It was synthesized and shown that it exhibits superconductivity (SC) with a critical temperature T c = 9.2 K [2], which is the highest T c recorded in this particular family. The experimental and theoretical results simultaneously indicate Mo 5 PB 2 to be a multiband superconductor like the widely studied high-T c compound MgB 2 [9,10].…”

Charge Transport in Heterostructures Based on Two-Gap Superconductors

“…Впоследствии оказалось, что MgB2 -не единственный сверхпроводник с двумя зонами и соответственно с двумя щелевыми особенностями. Свидетельства двухщелевой сверхпроводимости были обнаружены даже в таком достаточно тривиальном сверхпроводнике как свинец [3], а кроме того, в сплавах молибдена с рением [4], сложных соединениях Mo5PB2 [5], Mo8Ga41 [6] и RuB2 [7]. Основным доказательством наличия двух энергетических щелей являются эксперименты по измерению дифференциальной проводимости G(V) = dI(V)/dV гетероструктуры, образованной металлическим инжектором и сверхпроводником (S), которые образуют либо непосредственный контакт (контактная спектроскопия), либо разделены наноразмерной пленкой изолятора (I), сквозь которую электроны туннелируют согласно законам квантовой механики.…”