β-YbAlB4: A Critical Nodal Metal

We propose a model for the intrinsic quantum criticality of beta-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; m(J) = +/- 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 k(perpendicular to)(4) 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.