β-YbAlB4: A Critical Nodal Metal
Ramires, Aline; Coleman, Piers; Nevidomskyy, Andriy H.; Tsvelik, A. M.
We propose a model for the intrinsic quantum criticality of β-YbAlB4, in which a vortex in momentum space gives rise to a new type of Fermi surface singularity. The unquenched angular momentum of the |J=7/2,mJ=±5/2⟩ Yb 4f states generates a momentum-space line defect in the hybridization between 4f and conduction electrons, leading to a quasi-two-dimensional Fermi surface with a k4⊥ dispersion and a singular density of states proportional to E−1/2. We discuss the implications of this line node in momentum space for our current understanding of quantum criticality and its interplay with topology.