Microscopic characterization of “nematic ” precursor state of unconventional superconductivity in URu2Si2

In the superconducting state, two electrons form superconducting pairs. For the formation of pair electrons, an attractive interaction between electrons is necessary. In conventional superconductors, the origin of the attractive interaction is lattice vibration. In contrast, magnetic fluctuation is considered to be the origin in actinide superconducting compounds. Since high superconducting transition temperature Tc can be expected for a magnetic-fluctuation induced superconductor, it is important to clarify the mechanism of it. The heavy fermion superconductor URu2Si2 undergoes a second order phase transition at T0＝17.5 K. Since the order parameter of the transition has not ever been clearly identified, such order has been termed “hidden order”. As the superconducting transition occurs at lower Tc=1.5 K, the hidden order is precursor state of superconductivity. Owing to th