  Higher-order topological insulator (HOTI) represents a new phase of matter,
the characterization of which goes beyond the conventional bulk-boundary
correspondence and is attracting significant attention by the broad community.
Using a square-root operation, it has been suggested that a square-root HOTI
may emerge in a hybrid honeycomb-kagome lattice. Here, we report the first
experimental realization of the square-root HOTI in topological LC circuits. We
show theoretically and experimentally that the square-root HOTI inherits the
feature of wave function from its parent, with corner states pinned to non-zero
energies. The topological feature is fully characterized by the bulk
polarization. To directly measure the finite-energy corner modes, we introduce
extra grounded inductors to each node. Our results experimentally substantiate
the emerging square-root HOTI and pave the way to realizing exotic topological
phases that are challenging to observe in condensed matter physics.
