The effective increase in atomic scale disorder by doping and superconductivity in Ca ₃ Rh ₄ Sn ₁₃

Journal Article · Mon Oct 01 00:00:00 EDT 2018 · New Journal of Physics

DOI:https://doi.org/10.1088/1367-2630/aae4a8· OSTI ID:1477518

Ślebarski, A.; Zajdel, P.; Fijałkowski, M.; Maśka, M. M.; Witas, P.; Goraus, J.; Fang, Y.; Arnold, D. C.; Maple, M. B.

Here, a comprehensive study of the electronic structure, thermodynamic and electrical transport properties reveals the existence of inhomogeneous superconductivity due to structural disorder in Ca₃Rh₄Sn₁₃ doped with La (Ca_3–x La _x Rh₄Sn₁₃) or Ce (Ca_3–x Ce _x Rh₄Sn₁₃) with superconducting critical temperatures T_c* higher than those (T _c ) observed in the parent compounds. The T – x diagrams and the entropy S(x) T isotherms document well the relation between the degree of atomic disorder and separation of the high-temperature T_c* and T _c -bulk phases. In these dirty superconductors, with the mean free path much smaller than the coherence length, the Werthamer–Helfand–Hohenber theoretical model does not fit well the H _c2(T) data. We demonstrate that this discrepancy can result from the presence of strong inhomogeneity or from two-band superconductivity in these systems. Both the approaches very well describe the H – T dependencies, but the present results as well as our previous studies give stronger arguments for the scenario based on the presence of nanoscopic inhomogeneity of the superconducting state. A comparative study of La-doped and Ce-doped Ca₃Rh₄Sn₁₃ showed that in the disordered Ca_3–x Ce _x Rh₄Sn₁₃ alloys the presence of spin-glass effects is the cause of the additional increase of T_c* in respect to the critical temperatures of disordered Ca_3–x La _x Rh₄Sn₁₃. We also revisited the nature of structural phase transition at T* ~ 130 K and documented that there might be another precursor transition at higher temperatures. Raman spectroscopy and thermodynamic properties suggest that this structural transition may be associated with a CDW-type instability.

• Research Organization: Univ. of California, San Diego, La Jolla, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: NA0002909
• OSTI ID: 1477518
• Alternate ID(s): OSTI ID: 1483670
• Journal Information: New Journal of Physics, Journal Name: New Journal of Physics Vol. 20 Journal Issue: 10; ISSN 1367-2630
• Publisher: IOP Publishing
• Country of Publication: United Kingdom
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
superconductivity
atomic disorder
electronic band structure
thermodynamic and transport properties