The superconducting gap structure of recently discovered heavy fermion superconductor PrOs4Sb12 was investigated by using thermal transport measurements in magnetic field rotated relative to the crystal axes. We demonstrate that a novel change in the symmetry of the superconducting gap function occurs deep inside the superconducting state, giving a clear indication of the presence of two distinct superconducting phases with twofold and fourfold symmetries. We infer that the gap functions in both phases have a point node singularity, in contrast to the familiar line node singularity observed in almost all unconventional superconductors.
@article{arxiv.cond-mat/0209553,
title = {Multiple Superconducting Phases in New Heavy Fermion Superconductor PrOs4Sb12},
author = {K. Izawa and Y. Nakajima and J. Goryo and Y. Matsuda and S. Osaki and H. Sugawara and H. Sato and P. Thalmeier and K. Maki},
journal= {arXiv preprint arXiv:cond-mat/0209553},
year = {2009}
}