  Three-dimensional Dirac semimetals, a three-dimensional analogue of graphene,
are unusual quantum materials with massless Dirac fermions, which can be
further converted to Weyl fermions by breaking time reversal or inversion
symmetry. Topological surface states with Fermi arcs are predicted on the
surface and have been observed by angle-resolved photoemission spectroscopy
experiments. Although the exotic transport properties of the bulk Dirac cones
have been demonstrated, it is still a challenge to reveal the surface states
via transport measurements due to the highly conductive bulk states. Here, we
show Aharonov-Bohm oscillations in individual single-crystal Cd3As2 nanowires
with low carrier concentration and large surface-to-volume ratio, providing
transport evidence of the surface state in three-dimensional Dirac semimetals.
Moreover, the quantum transport can be modulated by tuning the Fermi level
using a gate voltage, enabling a deeper understanding of rich physics residing
in Dirac semimetals.
