Chiral singlet superconductivity in the weakly correlated metal LaPt3P
P. K. Biswas, S. K. Ghosh, J. Z. Zhao, D. A. Mayoh, N. D. Zhigadlo, Xiaofeng Xu, C. Baines, A. D. Hillier, G. Balakrishnan, M. R. Lees
Abstract
Abstract Chiral superconductors are novel topological materials with finite angular momentum Cooper pairs circulating around a unique chiral axis, thereby spontaneously breaking time-reversal symmetry. They are rather scarce and usually feature triplet pairing: a canonical example is the chiral p -wave state realized in the A -phase of superfluid He 3 . Chiral triplet superconductors are, however, topologically fragile with the corresponding gapless boundary modes only weakly protected against symmetry-preserving perturbations in contrast to their singlet counterparts. Using muon spin relaxation measurements, here we report that the weakly correlated pnictide compound LaPt 3 P has the two key features of a chiral superconductor: spontaneous magnetic fields inside the superconducting state indicating broken time-reversal symmetry and low temperature linear behaviour in the superfluid density indicating line nodes in the order parameter. Using symmetry analysis, first principles band structure calculation and mean-field theory, we unambiguously establish that the superconducting ground state of LaPt 3 P is a chiral d -wave singlet.