Circuit design and band structure of the 2D SSH topological circuit. (a) An illustration of a 2D SSH model containing 3×3 unit cells, which can be viewed as a dimerized 2D lattice with alternating hopping amplitude γ and γ’. (b) Unit cell of the 2D SSH circuit, obtained by replacing the potential well (black sphere) and two hopping amplitudes γ and γ’, respectively, with a capacitor and two different inductors. The inductances La and Lb indicate, respectively, the coupling strength between capacitors inside the unit cell (intracoupling) and between two adjacent unit cells (intercoupling). (c) 2D band structure theoretically calculated from the grounded circuit Laplacian of the periodic circuit model in (b) with the following circuit parameters: La=39nH, Lb=220nH, C=1000pF. (d) Band structure along the high symmetry lines and the numerically simulated absorption spectra on the bulk and edge sites. The frequency of the absorption peaks on both the bulk and edge sites coincides exactly with the band structure. (e) Band structure of the finite-sized 2D SSH circuit with 1×7.25 sites. The two curves located between the three bulk bandgaps indicate the existence of the nontrivial edge mode.