Nontrivial Fermi surface topology of the kagome superconductor CsV3Sb5 probed by de Haas–van Alphen oscillations

Abstract

We have investigated the normal state Fermi-surface properties of the kagome superconductor ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$ using torque magnetometry with applied fields ($H$) up to 35 T. The torque signal shows clear de Haas--van Alphen (dHvA) oscillations above 15 T. The oscillations are smooth and consist of seven distinct frequencies with values from $\ensuremath{\sim}$ 18 T to 2135 T. The presence of higher frequencies in ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$ is further confirmed by carrying out additional measurements using the tunnel diode oscillator technique. All frequencies measured at different tilt angles ($\ensuremath{\theta}$) of the field direction with respect to the c axis show a $1/\mathrm{cos}\ensuremath{\theta}$ dependence, implying that the Fermi surfaces corresponding to these frequencies are two dimensional (2D). The absence of dHvA oscillations at $\ensuremath{\theta}$ = ${90}^{o}$ further supports the presence of 2D Fermi surfaces. The Berry phase ($\ensuremath{\phi}$) determined from the Landau level fan diagram for all frequencies is $\ensuremath{\sim}$ 0.4. This value is close to the theoretical value of $\ensuremath{\phi}$ = 0.5 for a nontrivial system, which strongly supports the nontrivial topology of the Fermi surfaces of these frequencies. Several quantities characterizing the Fermi surface are calculated employing the Lifshitz-Kosevich theory. These findings are crucial for exploring the interplay between nontrivial band topology, charge-density wave, and unconventional superconductivity of ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$.