Fig. 1: Introducing KNLMs.
From: Tunable Octdong and Spindle-Torus Fermi Surfaces in Kramers Nodal Line Metals
a New phenomena arising from KNLMs. b Example of a typical Fermi-surface for a 3R phase of TMDCs with TRIMs indicated by red dots. c One of the three mirror planes delimited by the high-symmetry point F, where an example of the KNL connectivity is shown in red, together with the points of the Fermi surface intersecting the mirror plane of 3R-TaS2 shown in light blue. Notice that one KNL is pinned to the high symmetry direction Γ − T, while the almost-movable KNL is connecting L to F along an arbitrary path. d The quotient space of the mirror plane, where the opposite sides of the Brillouin zone are identified, is a torus (shown in gray), while the individual Fermi surface pockets that intersect the mirror plane (shown in blue) are 2-Tori T2. If the Fermi surfaces are pierced by a KNL, a touching point is enforced between the tori. Notice that, for simplicity, only the pockets intersecting the mirror plane are shown. e Open octdong Fermi surface, formed by an enforced touching between two pockets enclosing different TRIMs, and f open spindle-torus Fermi surface, with an enforced touching of two pockets enclosing the same TRIMs.
