Observation of negative longitudinal magnetoresistance in the type-II Dirac semimetal PtSe2

The negative longitudinal magnetoresistance (NLMR) was observed in type-II Dirac semimetal PtSe2 ultrathin microflakes. The NLMR disappeared when the magnetic field direction deviates from that of the electric field, or when the temperature is above a critical value, even when the Fermi level is away from Dirac point. The physical mechanism behind NLMR may relate to the chiral anomaly of Dirac fermions or the nontopological effect in PtSe2 material.