PrBi: Topology meets quadrupolar degrees of freedom

Novel materials incorporating electronic degrees of freedom other than charge, including spin, orbital, and valley degrees of freedom, have shown themselves to be of great interest and applicable potential. Recently, the multipolar degrees of freedom have attracted remarkable attention in the electronic correlated effects. In this work, we systematically study the transport, magnetic, and thermodynamic properties of the topological semimetal candidate PrBi in the framework of crystalline electric field theory. Our results demonstrate the Gamma(3) non-Kramers doublet as the ground state of Pr3+ (4f(2)) ions. This ground state is nonmagnetic but carries a nonzero quadrupolar moment <(O) over cap (0)(2)>. A quadrupolar phase transition is inferred below 0.08 K. No obvious quadrupolar Kondo effect can be identified. Ultrahigh-field quantum oscillation measurements confirm PrBi as a semimetal with a nontrivial Berry phase and low total carrier density 0.06/f.u. We discuss the interplay between low carrier density and 4f(2) quadrupolar moment, and ascribe the weak quadrupolar ordering and Kondo effect to consequences of the low carrier density. PrBi, thus, opens a new window to the physics of topology and strongly correlated effects with quadrupolar degrees of freedom in the low-carrier-density limit, evoking the need for a reexamination of the Nozieres exhaustion problem in the context of the multichannel Kondo effect.