  Recently, a new type of second-order topological insulator has been
theoretically proposed by introducing an in-plane Zeeman field into the
Kane-Mele model in the two-dimensional honeycomb lattice. A pair of topological
corner states arise at the corners with obtuse angles of an isolated
diamond-shaped flake. To probe the corner states, we study their transport
properties by attaching two leads to the system. Dressed by incoming electrons,
the dynamic corner state is very different from its static counterpart.
Resonant tunneling through the dressed corner state can occur by tuning the
in-plane Zeeman field. At the resonance, the pair of spatially well separated
and highly localized corner states can form a dimer state, whose wavefunction
extends almost the entire bulk of the diamond-shaped flake. By varying the
Zeeman field strength, multiple resonant tunneling events are mediated by the
same dimer state. This re-entrance effect can be understood by a simple model.
These findings extend our understanding of dynamic aspects of the second-order
topological corner states.
