Unconventional mesoscopic transport regimes in kagome magnets*

The kagome lattice is a versatile ingredient for realizing a range of exciting physical phenomena including flat bands, Dirac fermions, strong correlation, unconventional charge density waves, and superconductivity. Specifically, materials hosting such lattice structures, such as kagome magnets and superconductors, have demonstrated anomalous transport properties, such as strange metallic resistivity and anisotropic magnetic susceptibilities. One transport aspect that is underexplored is the possibility of realizing a hydrodynamic regime for electron fluid formation. The kagome magnets TbMn₆Sn₆ (a Chern ferrimagnet) and Mn₃Ge (a Weyl semimetal antiferromagnet) have interesting electronic and thermal conductivities, with the two showing large and opposing deviations from the Wiedemann-Franz law and Mott relation. Herein, we study whether such conductivities can be decoupled into independent diffusive modes and explore the possible emergence of hydrodynamics in finite channel geometries using a combination of ab initio calculations and numerical simulations of the Boltzmann transport equation. Our work aims to rationalize the transport of kagome magnets by resolving their temperature-dependent electron and phonon scattering mechanisms and exploring their interplay with quasiparticle mean free paths and Fermi surface topologies.