Anisotropic magnetic fluctuations in YbRhSi

Kambe, Shinsaku  ; Sakai, Hironori   ; Tokunaga, Yo  ; Lapertot, G.*; Matsuda, Tatsuma*; Knebel, G.*; Flouquet, J.*; Walstedt, R. E.*

Recently there is renewed interest in quantum critical phase transitions (QCPT) at K in metallic strongly-correlated electron systems. From early experimental results, the QCPT in the Kondo-lattice compound YbRhSi is not a case of the ordinary spin density wave (SDW) instability observed in Ce-based Kondo-lattices, but a candidate for a novel locally critical case In new observations reported here, we find that coexisting, static Fermi liquid (FL) and non-Fermi liquid (NFL) states are a key feature of the QCPT in YbRhSi. Such a pair of states has remained hidden in Ce compounds, owing presumably to short lifetimes for the two states. A new scaling law for the occupation ratio of the two states is derived, and could be widely applicable to Kondo-lattice systems.