Tunable line node semimetals

Weyl semimetals are examples of a new class of topological states of matter, which are gapless in the bulk with protected surface states. Their low-energy sector is characterized by massless chiral fermions, which are robust against translationally invariant perturbations. A variant of these systems has two nondegenerate bands touching along lines rather than points. A proposal to realize such a phase involves alternating layers of topological insulators and magnetic insulators, where the magnetization lies perpendicular to the symmetry axis of the heterostructure. The shape, size, and the dispersion in the vicinity of the nodal lines varies with the strength of the magnetization, offering a new knob to control the properties of the system. In this paper, we map out the evolution of the nodal lines and the dependence of the conductivity on magnetization and identify signatures of the low-energy sector in quantum oscillation measurements.