Suppression of time reversal symmetry breaking superconductivity in Pr(Os,Ru)4Sb12 and (Pr,La)Os4Sb12
Abstract
Zero-field muon spin relaxation experiments have been carried out in the Pr(Os1-xRux)4Sb12 and Pr1-yLayOs4Sb12 alloy systems to investigate broken time-reversal symmetry (TRS) in the superconducting state, signaled by the onset of a spontaneous static local magnetic field Bs. In both alloy series Bs initially decreases linearly with solute concentration. Ru doping is considerably more efficient than La doping, with a ~50% faster initial decrease. The data suggest that broken TRS is suppressed for Ru concentration x >~ 0.6, but persists for essentially all La concentrations. Our data support a crystal-field excitonic Cooper pairing mechanism for TRS-breaking superconductivity.
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