CeRh₂As₂: Heavy fermions and unusual orders

The anomalous properties of actinide and lanthanide inter-metallics results from the fact that the f-states partially preserve their atomic character while giving rise to strongly renormalized bands. As a results, one observes a plethora of unusual states at low temperatures. A prominent example is CeRh₂As₂ [1] where multi-phase superconductivity seems to develop inside a normal state whose order is still unclear. Thermodynamic and magnetic measurements seem to indicate a non-magnetic state with multipolar order [2] while antiferromagnetic (AFM) order, however, was clearly detected by μSR and NQR/NMR [3] experiments. The present talk focusses on the instabilities of the strongly renormalized Fermi liquid

state in the heavy-fermion compound CeRh2As2. The narrow quasiparticle bands which arise from the Ce-4f degrees of freedom via the Kondo effect are calculated by means of the Renormalized Band (RB) method. A simplified model band structure is used to calculate the momentum-dependent multipolar susceptibilities. We conjecture that the Kondo-induced quasi-quartet CEF ground state [4] in combination with pronounced nesting features of the Fermi surface may give rise to ordered states involving multipolar degrees of freedom [3,4].

 

[1] S. Khim et al., Science 373, 1012 (2021)

[2] P.Khanenko et al., Phys. Rev. B 111, 045162 (2025)

[3] Seunghyun Khim et al., Phys. Rev. B 111, 115134 (2025)

[4] D. Christovam et al, Physics. Rev. Lett. 132, 046401 (2024)