Polymorphic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>PtBi</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>: Growth, structure, and superconducting properties
G. Shipunov, I. Kovalchuk, B. R. Piening, V. Labracherie, A. Veyrat, D. Wolf, A. Lubk, S. Subakti, R. Giraud, J. Dufouleur, S. Shokri, F. Caglieris, C. Hess, D. V. Efremov, B. Büchner, S. Aswartham
Abstract
${\mathrm{PtBi}}_{2}$ is a polymorphic system with interesting electronic properties. Here we report optimized crystal growth and structural characterization of pyrite-type and trigonal modification of ${\mathrm{PtBi}}_{2}$. Selected area electron diffraction, x-ray powder diffraction, and further Rietveld refinement confirms that trigonal ${\mathrm{PtBi}}_{2}$ crystallizes in the noncentrosymmetric $P31m$ space group, and pyrite-type ${\mathrm{PtBi}}_{2}$ crystallizes in the $Pa\overline{3}$ space group. A series of ${\mathrm{Pt}}_{1\ensuremath{-}x}{\mathrm{Rh}}_{x}{\mathrm{Bi}}_{2}$ samples was obtained for $x=0,0.03,0.35$ in the trigonal ${\mathrm{PtBi}}_{2}$ structure. These ${\mathrm{Pt}}_{1\ensuremath{-}x}{\mathrm{Rh}}_{x}{\mathrm{Bi}}_{2}$ compounds become superconducting where the critical temperature increases from ${T}_{c}=600$ mK for $x=0$ up to ${T}_{c}=2.7$ K for $x=0.35$. Furthermore, we calculate the electronic band structure using the obtained structure parameters. The calculated density of states shows a minimum for the stoichiometric compound at the Fermi level. These findings warrant further research using a broader array of experimental techniques, as well as on the effect of the substitution on the nontrivial band structure.