  The relativistic massless charge carriers with a Fermi velocity of about c300
in graphene enable us to realize two distinct types of resonances (c, the speed
of light in vacuum). One is electron whispering-gallery mode in graphene
quantum dots arising from the Klein tunneling of the massless Dirac fermions.
The other is atomic collapse state, which has never been observed in experiment
with real atoms due to the difficulty of producing heavy nuclei with charge Z
170, however, can be realized near a Coulomb impurity in graphene with a charge
Z 1 because of the small velocity of the Dirac excitations. Here, unexpectedly,
we demonstrate that both the electron whispering-gallery modes and atomic
collapse states coexist in grapheneWSe2 heterostructure quantum dots due to the
Coulomb-like potential near their edges. By applying a perpendicular magnetic
field, evolution from the atomic collapse states to unusual Landau levels in
the collapse regime are explored for the first time.
