Berry curvature induced anisotropic magnetotransport in a quadratic triple-component fermionic system

Abstract

Triple-component fermions are pseudospin-1 quasiparticles hosted by certain three-band semimetals in the vicinity of their band-touching nodes [Phys. Rev. B {\bf 100}, 235201 (2019)]. The excitations comprise of a flat band and two dispersive bands. The energies of the dispersive bands are $E_{\pm}=\pm\sqrt{\alpha^2_n k^{2n}_\perp+v^2_z k^2_z}$ with $k_\perp=\sqrt{k^2_x+k^2_y}$ and $n=1,2,3$. In this work, we obtain the exact expression of Berry curvature, approximate form of density of states and Fermi energy as a function of carrier density for any value of $n$. In particular, we study the Berry curvature induced electrical and thermal magnetotransport properties of quadratic $(n=2)$ triple-component fermions using semiclassical Boltzmann transport formalism. Since the energy spectrum is anisotropic, we consider two orientations of magnetic field (${\bf B}$): (i) ${\bf B}$ applied in the $x$-$y$ plane and (ii) ${\bf B}$ applied in the $x$-$z$ plane. For both the orientations, the longitudinal and planar magnetoelectric/magnetothermal conductivities show the usual quadratic-$B$ dependence and oscillatory behaviour with respect to the angle between the applied electric field/temperature gradient and magnetic field as observed in other topological semimetals. However, the out-of-plane magnetoconductivity has an oscillatory dependence on angle between the applied fields for the second orientation but is angle-independent for the first one. We observe large differences in the magnitudes of transport coefficients for the two orientations at a given Fermi energy. A noteworthy feature of quadratic triple-component fermions which is typically absent in conventional systems is that certain transport coefficients and their ratios are independent of Fermi energy within the low-energy model.