Electrons' charge, spin, orbital degrees of freedom, and phonons constitute the fundamental building blocks of correlated quantum matters. The complex interplay among them renders exotic emergent phenomena that push the boundaries of our knowledge about the quantum world. Though earlier studies essentially focus on the role of spin in generating quantum phases and fluctuations, designing novel quantum phases with alternative ingredients other than spin may inspire a new conceptual framework for understanding confounding quantum phenomena in strongly correlated electron systems [1-3]. 

Entanglement between multipolar moments and conduction electrons paves a new route to extend the landscape of novel quantum phenomena beyond the spin-only paradigm. A model platform for exploring multipolar physics is the cubic heavy-fermion system PrTr₂Al₂₀ (Tr = Ti, V). This system features a nonmagnetic ground state in which the magnetic dipolar moment (spin) is absent, but higher-rank multipolar moments (quadrupoles and octupoles) are active [4]. The entanglement of these local multipolar moments with conduction electrons results in a rich phase diagram comprising multipolar orders, non-Fermi liquid (NFL) phase, and exotic superconductivity [4-6]. In this talk, I will present our experimental investigation into the multipolar ordered phases and magnetic-field-induced quantum critical behavior in PrV₂Al₂₀ via a combination of electrical transport, thermodynamics, and lattice probes, which shows that the evolution of ordered phases, non-Fermi liquid behavior, and Fermi surface across the multipolar quantum critical regime drastically differs from that in the familiar magnetic setting.

References

[1] S. Paschen and Q. Si, Nat. Rev. Phys. 3, 9-26 (2021)

[2] P.W. Phillips, N.E. Hussey, and P. Abbamonte, Science 377, (2022)

[3] A. E. Böhmer, J-H Chu, S. Lederer and M. Yi, Nat. Phys. 18, 1412-1419 (2022)

[4] A. Sakai and S. Nakatsuji, J. Phys. Soc. Jpn. 80, 063701 (2011)

[5] K. Matsubayashi et al., Phys. Rev. Letts. 109, 187004 (2012)

[6] Y. Shimura et al Phys. Rev. B. 91, 241102(R)