Final Report Summary - NEWHEAVYFERMION (Novel materials and extreme conditions to open new frontiers in heavy fermion physics)
The target of this project is to develop new materials of heavy fermion system and to explore the novel phenomena by high quality single crystals and the precise experiments under extreme conditions, namely low temperature, high field and high pressure. We focus on the ferromagnetic superconductors, such as URhGe, UCoGe and UGe2. The unusual field-reinforced superconductivity was found when the field applied along the hard magnetization axis in UCoGe and URhGe. Furthermore the collapse of Curie temperature and the Fermi surface reconstruction give the solid evidence that the ferromagnetic fluctuations and Fermi surface instabilities including Lifshitz transition play important roles for superconductivity. In the hidden order system, URu2Si2, we have clarified the Fermi surface both in the hidden order state and in the antiferromagnetic state. The ferromagnetic quantum criticality and its critical end point were also studied in details on UGe2, UCoAl and URhAl.