TRR 360 Seminar:

Hidden multipolar order and singlet magnetism in f-electrons systems

Sergii Khmelevskyi

Hidden multipolar order and singlet magnetism in f-electrons systems

Dr. Sergii Khmelevskyi

TU Wien

The nature of order in low-temperature phases of some materials is not directly seen by experiment. Such “hidden orders” (HOs) may inspire decades of research to identify the mechanism underlying those exotic states of matter. In insulators, HO phases originate in degenerate many-electron states on localized f-shells that may harbor high-rank multipole moments. We show how the ground-state order and magnetic excitations of a prototypical HO system NpO₂, can be fully described by a low-energy Hamiltonian derived by a many-body ab initio force theorem method. A primary non collinear order of time odd rank 5 (triakontadipolar) moments has been predicted. We show also that exotic non-chiral magnetic order in PrO₂ is a results of a strong high order multipolar interactions within whole |JM> ground state multiplet. The multipolar interactions also leads to the peculiar magnetization process in PrO₂ resulting in the exotic meta-magnetic transition in the applied magnetic field and fully dominate the ordinary dipolar Heisenberg exchange.

As has been shown by Kotliar and Haule in 2007 the canonical and perhaps most investigated metallic “hidden” order materials URu₂Si₂ can also develop a “hidden” multipolar order (hexadecapolar) due to localized 5f² configuration at low temperature. Whereas at higher temperatures a hybridization of the localized 5f-levels leads to the Kondo behavior (“Kondo arrest scenario”) and at very low temperature a hidden order phase coexists with superconductivity. We reveal on basis of correlated ab-intio calculations a close analogy between normal state behavior of URu₂Si₂ and newly discovered heavy fermion UTe₂ superconductor.