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Dirac semimetals transform into Weyl semimetals by breaking the time reversal symmetry, resulting in interesting physical properties, such as the chiral anomaly induced negative magnetoresistance and the Weyl orbit related quantum transport. Here, we report the disappearance of the Weyl semimetal phase in Dirac semimetal Cd3As2 nanoplates with a (112) surface plane when applying a perpendicular high magnetic field. The Landau fan extracted from the notable quantum oscillations shows the nontrivial Berry phase π for B<9.4 T and its disappearance at around 1/B∼0.1 T−1. Our observations indicate the topological phase transition from nontrivial states to gap-opening states induced by the C4 rotational symmetry breaking under a high magnetic field.

Dirac semimetals possess Fermi-arc surface states, which will be a set of discrete surface subbands in a nanowire due to the quantum confinement effect. Here, we report a tunable Fano effect induced by the interference between the discrete surface states and continuous bulk states of a Dirac semimetal Cd_{3}As_{2} nanowire. The discrete surface bands lead to a zero bias peak in conductance as the Femi level is tuned to across the surface subbands. The Fano resonance results in an asymmetric line shape in the differential conductance dI/dV spectrum. Furthermore, the Fano interference would introduce an additional phase into the Weyl orbits and lead to a modification of the oscillation frequency. The results are valuable for further understanding the exotic quantum transport properties of topological semimetals.