A New Noncentrosymmetric Superconducting Phase in the Li--Rh--B System

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Superconductivity, at 2--3 K, was observed in a novel phase of the ternary Li--Rh--B system. The structural phase exhibits a large noncentrosymmetric cubic unit cell with the a-parameter being within 1.208\leq a\leq 1.215 nm. This phase is stable over a wider compositional range of LixRhBy (0.6<x<2,1<y<2). The superconductivity, as well as the unit cell volume, is sensitive to the Li/B content but it is manifested with T_{\text{c}}\geq 1.8 K over a wider compositional range: the highest T_{\text{c}}\simeq 3 K occurs for x:y\approx 0.9:1.5 with a\simeq 1.209 nm. The superconducting shielding fraction of most samples is almost 80% of that of Sn. The lower critical field, H_{\text{c1}}(0), is {\sim}65 Oe while the upper one, H_{\text{c2}}(0) is determined from extrapolation to be higher than 14 kOe. We discuss the influence of pressure on T_{\text{c}} and also the influence of the lack of inversion symmetry on the superconducting properties.
2011-01-15