Magnetoconductivity and quantum oscillations in intercalated graphite CaC$_6$ with the Fermi surface reconstructed by the uniaxial charge density wave

Abstract

We report a magnetoconductivity tensor $\sigma$ for the intercalated graphite CaC$_6$, in the ground state of the uniaxial charge density wave (CDW), under conditions of coherent magnetic breakdown due to strong external magnetic field $B$ perpendicular to the conducting plane. The uniaxial charge density wave reconstructs initially closed Fermi surface into an open one, accompanied with formation of a pseudo-gap in the electron density of states around the Fermi energy. The magnetoconductivity tensor is calculated within the quantum density matrix and semiclassical magnetic breakdown approach focused on modification of the main, so-called classical contribution to magnetoconductivity by magnetic breakdown, neglecting the higher order corrections. In the presence of magnetic breakdown, in spite of open Fermi surface configuration, all classical magnetoconductivity components, the one along the CDW apex $\sigma_{xx} \sim 1/B^2$, perpendicular to the CDW apex $\sigma_{yy} \sim const$, as well as the Hall conductivity $\sigma_{xy} \sim 1/B$, undergo strong quantum oscillations vs. inverse magnetic field. Those oscillations do not appear as a mere additive correction, but rather alter the classical result becoming an inherent part of it, turning it to essentially non-classical.