High-field Fermi surface properties in the low-carrier heavy-fermion compound URuSi

Aoki, Dai*; Knebel, G.*; Sheikin, I.*; Hassinger, E.*; Malone, L.*; Matsuda, Tatsuma; Flouquet, J.*

We performed the Shubnikov-de Haas (SdH) experiments of the low-carrier heavy-fermion compound URuSi at high fields up to 34T and at low temperatures down to 30 mK. All main SdH branches named and and were observed for all the measured field-directions, indicating that they are attributed to the closed Fermi surfaces with nearly spherical shapes. An anomalous split of branch was detected for the field along the basal plane; the split immediately disappeared by tilting the field to [001] direction, implying a fingerprint of the hidden order state. High-field experiments reveal the complicated field-dependence of the SdH frequencies and the cyclotron masses due to the Zeeman spin-splitting associated with the Fermi surface reconstruction in the hidden order state with small carrier numbers. A new SdH branch named with a large cyclotron mass of 25 was detected at high fields above 23T close to hidden order instabilities.