Non-abelian topology of nodal-line rings in $\mathcal{P}\mathcal{T}$-symmetric systems

Apoorv Tiwari, Tomáš Bzdušek

Nodal lines inside the momentum space of three-dimensional crystalline solids are topologically stabilized by a $\pi$-flux of Berry phase. Nodal-line rings in $\mathcal{P}\mathcal{T}$-symmetri…