Research / 2018 / Article / Fig 1

Research Article

Topological Nodal States in Circuit Lattice

Figure 1

Schematic setup of the three-dimensional LC circuit lattice. (a) Honeycomb layers consisting of inductors and capacitors stack along direction without connection between each layer. The primitive unit cell consists of two inequivalent nodes A and B, which are linked by capacitors , , and in the - plane. Each node () is grounded through the parallel connected inductor () and capacitor (). Lattice vectors are denoted as , and . The frequency bands structure of the single layer honeycomb LC lattice has two band-crossing points, which are uniform in direction and form two straight nodal lines in the BZ (red colour lines in the inset). (b) Connecting nodes A and nodes B between neighbor-layers with . The nodal lines become dependent and form a closed ring by choosing appropriate . (c) Connecting nodes A-A and nodes B-B between neighbor-layers with and , respectively, and removing the space inversion symmetry by tuning and , the nodal ring may be degenerated to Weyl points. The LC lattice can be deformed into (d), which brings convenience for constructing circuit elements in experiments with spectrum topologically invariable.