Fig. 4: Schematic illustration of the two-dimensional topolectrical circuit.
From: Gauge-dependent topology in non-reciprocal hopping systems with pseudo-Hermitian symmetry
a Two unit cells in the circuit lattice. The reciprocal hopping terms are realized by capacitors Cm, and the non-reciprocal hopping terms are realized by the operational amplifiers and capacitors Cγ, where current flow can exist between A sites and the output of the amplifier, but cannot exist between B sites and the input of the amplifier. The LC-circuits which connect the A/B sites and the ground provide the on-site frequency response. b The 40 × 40 lattice contains 80 sub-circuits, and each sub-circuit contains 20 unit cells, arranged along y direction. The schematic view shows the connection between two sub-circuits along x direction, where An, Bn denote the sites of the nth unit cell inside the sub-circuit, and the connection between the unit cells is the same as (a).
