Quantum Oscillations and Electronic Structure in the Large-Chern-Number Topological Chiral Semimetal PtGa

We report the magnetoresistance (MR), de Haas-van Alphen (dHvA) oscillations and the electronic structures of single-crystal PtGa. The large unsaturated MR is observed with the magnetic field B \parallel 111. Evident dHvA oscillations with the B \parallel 001 configuration are observed, from which twelve fundamental frequencies are extracted and the spin-orbit coupling (SOC) induced band splitting is revealed. The light cyclotron effective masses are extracted from the fitting by the thermal damping term of the Lifshitz–Kosevich formula. Combining with the calculated frequencies from the first-principles calculations, the dHvA frequencies F_1/F_3 and F_11/F_12 are confirmed to originate from the electron pockets at \mit\Gamma and R, respectively. The first-principles calculations also reveal the existence of spin-3/2 Rarita–Schwinger–Weyl fermions and time-reversal doubling of the spin-1 excitation at \mit\Gamma and R with large Chern numbers of \pm4 when SOC is included.