  Higher-order topological phase in 2-dimensional (2D) systems is characterized
by in-gap corner states, which are hard to detect and utilize. We numerically
investigate transport properties of topological corner states in 2D honeycomb
lattice, where the second-order topological phase is induced by an in-plane
Zeeman field in the conventional Kane-Mele model. Through engineering
multihollow structures with appropriate boundaries in honeycomb lattice,
multiple corner states emerge, which greatly increases the probability to
observe them. A typical two-probe setup is built to study the transport
features of a diamond-shaped system with multihollow structures. Numerical
results reveal the existence of global resonant states in bulk insulator, which
corresponds to the resonant tunneling of multiple corner states and occupies
the entire scattering region. Furthermore, based on the well separated energy
levels of multiple corner states, a single-electron source is constructed.
