Non-Monotonic Evolution of Carrier Density and Mobility under Thermal Cycling Treatments in Dirac Semimetal Cd_3As_2 Microbelts

Tunable carrier density plays a key role in the investigation of novel transport properties in three-dimensional topological semimetals. We demonstrate that the carrier density, as well as the mobility, of Dirac semimetal Cd_3As_2 nanoplates can be effectively tuned via in situ thermal treatment at 350 K for one hour, resulting in non-monotonic evolution by virtue of the thermal cycling treatments. The upward shift of Fermi level relative to the Dirac nodes blurs the surface Fermi-arc states, accompanied by an anomalous phase shift in the oscillations of bulk states, due to a change in the topology of the electrons. Meanwhile, the oscillation peaks of bulk longitudinal magnetoresistivity shift at high fields, due to their coupling to the oscillations of the surface Fermi-arc states. Our work provides a thermal control mechanism for the manipulation of quantum states in Dirac semimetal Cd_3As_2 at high temperatures, via their carrier density.