Quantum Oscillations and Electronic Structure in the Large-Chern-Number Topological Chiral Semimetal PtGa*Supported by the National Key Research and Development Program of China (Grant Nos. 2019YFA0308602, 2018YFA0305700 and 2016YFA0300600), the National Natural Science Foundation of China (Grant Nos. 11874422 and 11574391), the Fundamental Research Funds for the Central Universities, and the Research Funds of Renmin University of China (Grant Nos. 19XNLG18

Abstract

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 ∥ [111]. Evident dHvA oscillations with the B ∥ [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 F1/F3 and F11/F12 are confirmed to originate from the electron pockets at Γ 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 Γ and R with large Chern numbers of ± 4 when SOC is included.