  We experimentally investigate the charge (isospin) frustration induced by a
geometrical symmetry in a triangular triple quantum dot. We observe the
ground-state charge configurations of six-fold degeneracy, the manifestation of
the frustration. The frustration results in omnidirectional charge transport,
and it is accompanied by nearby nontrivial triple degenerate states in the
charge stability diagram. The findings agree with a capacitive interaction
model. We also observe unusual transport by the frustration, which might be
related to elastic cotunneling and the interference of trajectories through the
dot. This work demonstrates a unique way of studying geometrical frustration in
a controllable way.
