Discovery of Superconductivity in Nb$_4$SiSb$_2$ with a V$_4$SiSb$_2$-Type Structure and Implications of Interstitial Doping on its Physical Properties

Manuele D. Balestra; Omargeldi Atanov; Robin Lefèvre; Olivier Blacque; Yat Hei Ng; Rolf Lortz; Fabian O. von Rohr

doi:10.1039/D2TC01510B

paper

Discovery of Superconductivity in Nb $_{4}$ SiSb $_{2}$ with a V $_{4}$ SiSb $_{2}$ -Type Structure and Implications of Interstitial Doping on its Physical Properties

arXiv:2208.04834 · doi:10.1039/D2TC01510B

Abstract

We report on the discovery, structural analysis, and the physical properties of Nb $_{4}$ SiSb $_{2}$ -- a hitherto unknown compound crystallizing in the V $_{4}$ SiSb $_{2}$ -type structure with the tetragonal space group $I 4/ m c m$ and unit cell parameters $a$ = 10.3638(2) $A ˚$ and $c$ = 4.9151(2) $A ˚$ . We find Nb $_{4}$ SiSb $_{2}$ to be a metal undergoing a transition to a superconducting state at a critical temperature of $T_{c} \approx$ 1.6 K. The bulk nature of the superconductivity in this material is confirmed by the observation of a well defined discontinuity in specific heat with a normalized specific heat jump of $Δ C (T_{c}) / γ T_{c} = 1.33 mJ mol^{- 1} K^{- 2}$ . We find that for Nb $_{4}$ SiSb $_{2}$ , the unoccupied sites on the $4 b$ Wyckoff position can be partially occupied with Cu, Pd, or Pt. Low-temperature resistivity measurements show transitions to superconductivity for all three compounds at $T_{c} \approx 1.2 K$ for Nb $_{4}$ Cu $_{0.2}$ SiSb $_{2}$ , and $T_{c} \approx 0.8 K$ for Nb $_{4}$ Pd $_{0.2}$ SiSb $_{2}$ as well as for Nb $_{4}$ Pt $_{0.14}$ SiSb $_{2}$ . The addition of electron-donor atoms into these void positions, henceforth, lowers the superconducting transition temperature in comparison to the parent compound.

Discovery of Superconductivity in Nb4​SiSb2​ with a V4​SiSb2​-Type Structure and Implications of Interstitial Doping on its Physical Properties

Abstract

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Discovery of Superconductivity in Nb $_{4}$ SiSb $_{2}$ with a V $_{4}$ SiSb $_{2}$ -Type Structure and Implications of Interstitial Doping on its Physical Properties