Upper critical field H_c2 in PrOs4Sb12

Abstract

We study the upper critical field of the A and B phases in the triplet superconductor PrOs_{4}Sb_{12} within the p+h-wave superconductivity proposed recently for this material. The present result is compared with H_{c2}(t) and H*(t), the boundary between the A and B phase in PrOs_{4}Sb_{12}, reported earlier and with more recent data of H$_{c2}(t)$ for the single phase crystal. We find H_{c2}(t)'s for both the two phase crystal and the single phase crystal are described by the model for the A phase. From this fitting one can deduce the Fermi velocity as v=2.5 x 10^6 cm/s. On the other hand H_{c2}(t) for the B phase is found to be somewhat smaller than H*(t), which is rather puzzling.