Polycrystalline samples of four intermetallic compounds: MV2Al20 (M = Sc, Y, La, and Lu) were synthesized using an arc-melting technique. The crystal structures were analyzed by means of powder x-ray diffraction and Rietveld analysis, and the physical properties were studied by means of heat capacity, electrical resistivity and magnetic susceptibility measurements down to 0.4 K. For ScV2Al20, LuV2Al20, and YV2Al20, superconductivity was observed with critical temperatures Tc = 1.00 K, 0.57 K, and 0.60 K, respectively. Superconductivity for the Lu compound is reported for the first time. Theoretical calculations of the electronic and phonon structures were conducted in order to analyze the superconductivity and dynamics in ScV2Al20, YV2Al20, and LuV2Al20 and to explain the lack of a superconducting transition in LaV2Al20 down to 0.4 K. The results of the experimental and theoretical studies show that all the compounds are weakly-coupled type II BCS superconductors, and reveal the importance of the M-atom anharmonic "rattling" modes for the superconductivity in these materials, which seem to enhance Tc, especially for ScV2Al20.
@article{arxiv.1603.05320,
title = {Rattling enhanced superconductivity in MV$_2$Al$_{20}$ (M = Sc, Lu, Y) intermetallic cage compounds},
author = {Michał J. Winiarski and Bartłomiej Wiendlocha and Małgorzata Sternik and Piotr Wiśniewski and James R. O'Brien and Dariusz Kaczorowski and Tomasz Klimczuk},
journal= {arXiv preprint arXiv:1603.05320},
year = {2016}
}
Comments
34 pages (+ supplemental material), 15 figures (+ 4 in suppl. mat.); Accepted for publication in Physical Review B