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 = \pm5/2> 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\perp4 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.
@article{arxiv.1207.6441,
title = {{\beta}-YbAlB4: a critical nodal metal},
author = {Aline Ramires and Piers Coleman and Andriy H. Nevidomskyy and A. M. Tsvelik},
journal= {arXiv preprint arXiv:1207.6441},
year = {2012}
}