de Haas–van Alphen quantum oscillations and electronic structure in the large-Chern-number topological chiral semimetal CoSi

Abstract

We investigate the magnetic transport properties and electronic structures of single crystal CoSi via angle-dependent quantum oscillation measurements. Prominent de Haas--van Alphen oscillations have been observed with the magnetic field tilting from $B\ensuremath{\parallel}[001]$ to $B\ensuremath{\parallel}[110]$, from which three fundamental frequencies are extracted. The low frequency ${F}_{\ensuremath{\alpha}}$, first observed in quantum oscillations, presents the contribution from the hole pocket at the Brillouin zone (BZ) center $\mathrm{\ensuremath{\Gamma}}$ point. Two high frequencies ${F}_{\ensuremath{\beta}}$ and ${F}_{\ensuremath{\gamma}}$, accompanied with asymmetrical peaks in the fast Fourier-transform spectra, are confirmed to stem from the electron pockets with spin-orbit coupling (SOC) at the BZ corner $R$ point. Combined with the analysis of first-principles calculations, the asymmetry of peaks originate from the SOC-induced band splitting when $B\ensuremath{\parallel}[110]$ and the irregular Fermi pockets when $B\ensuremath{\parallel}[001]$, respectively.