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| ai.viXra.org > Condensed Matter > 2610 |
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[2] ai.viXra.org:2610.0066 [pdf] submitted on 2026-10-29 03:57:00
Authors: Ipsita Mandal
Comments: 96 Pages.
We present an exact solution of the linearised semiclassical Boltzmann equation (SBE) beyond the relaxation-time approximation for multifold semimetals under arbitrarily oriented electric and magnetic fields. The framework treats the Berry curvature, orbital magnetic moment, Lorentz-force operator, and scattering terms on equal footing. Momentum-independent scattering-amplitudes couple the Fermi-surface sheets through intranode, interband, and internode processes. The scattering kernel has a finite rank and the SBE reduces to a linear system for a few moments, which is closed by the electron-number constraint. We apply this approach to four systems involving quadratic-corrected triple-point, Weyl, and Rarita-Schwinger-Weyl nodes, including tilted triple-point nodes. We obtain analytical results at zero field and to leading orders in the magnetic field, alongside numerical solutions for the full field dependence. Our results elucidate the roles of the topological properties, Lorentz-force operator, tilt, and intra- and internode scatterings in shaping the magnetoconductivity and planar-Hall response for noncollinear fields. It cures severe shortcomings of previous treatments like incomplete ansätze and incomplete treatment of the Lorentz-force operator.
Category: Condensed Matter
[1] ai.viXra.org:2610.0038 [pdf] submitted on 2026-10-16 09:52:32
Authors: Ipsita Mandal
Comments: 42 Pages.
We investigate collective charge excitations in three-dimensional multifold semimetals in which multiple bands cross the Fermi level at a positive chemical potential, focusing on pseudospin-3/2 Rarita—Schwinger—Weyl semimetals and on Kramers—Weyl semimetals. Both systems host multiple concentric Fermi surfaces at positive chemical potential. Within the random-phase approximation, we analyse the density response, Drude weights, dielectric function, plasmon modes and their Landau damping, and Friedel oscillations, considering both small and arbitrary momentum transfers. In our companion work, href{https://arxiv.org/abs/2610.18629}{arXiv:2610.18629}, we investigated pseudospin-1 triple-point semimetals, with and without a quadratic correction to their dispersion, as well as Hopf and Weyl semimetals. Comparing these systems allows us to elucidate the distinct roles of band dispersions and eigenstates in shaping collective charge dynamics. Our results demonstrate that collective charge excitations can distinguish multifold nodes with multiple Fermi surfaces and reveal information encoded in their eigenstates beyond that contained in the single-particle dispersion.
Category: Condensed Matter