Lorentz ratio of a compensated metal

Abstract

A violation of the Wiedemann-Franz law in a metal can be quantified by comparing the Lorentz ratio, L = κρ/T , where κ is the thermal conductivity and ρ is the electrical resistivity, with the universal Sommerfeld constant, L0 = (π 2 /3)(kB/e) 2 . We obtain the Lorentz ratio of a clean compensated metal with intercarrier interaction as the dominant scattering mechanism by solving exactly the system of coupled integral Boltzmann equations. The Lorentz ratio is shown to assume a particular simple form in the forward-scattering limit: L/L0 = Θ 2 /2, where Θ is the scattering angle. In this limit, L/L0 can be arbitrarily small. We also show how the same result can be obtained without the benefit of an exact solution. We discuss how a strong downward violation of the Wiedemann-Franz law in a type-II Weyl semimetal WP2 can be explained within our model.

Magnetization-governed magnetoresistance anisotropy in the topological semimetal CeBi

“…Magnetization measurements revealed rich magnetic phases including antiferromagnetic, ferrimagnetic and ferromagnetic phases, depending on temperature and magnitude of the magnetic field [41,45]. In the context of topological materials, CeBi recently has attracted renewed interest as it has been identified to be a topological semimetal in angleresolved photoemission spectroscopy (ARPES) experiments [38,47]. It is also the only known magnetic topological semimetal that shows extremely large magnetoresistance (XMR) [47].…”

“…In the context of topological materials, CeBi recently has attracted renewed interest as it has been identified to be a topological semimetal in angleresolved photoemission spectroscopy (ARPES) experiments [38,47]. It is also the only known magnetic topological semimetal that shows extremely large magnetoresistance (XMR) [47].…”

“…Although magnetotransport measurements were conducted more than 20 years ago and anomalous Hall effects were also observed [48], MR investigations have been only reported in the form of temperature dependence of the resistance R(T) at low magnetic fields (up to 3.7 T) [48] or at a high magnetic field of 9 T [47]. Furthermore, the magnetic field in both cases was applied along a primary crystalline axis.…”

“…The expected [41,48] paramagnetic to antiferromagnetic (AFM) transition at TN » 25 K and the transition from type I AFM to type IA AFM at TN/2 (» 12.8 K), upon cooling, can be clearly identified (see Fig.S1b for schematics on magnetic structures). CeBi has a rock-salt cubic crystal lattice, resulting in identical electronic structures along the kx, ky and kz directions of the Brillouin zone [47]. Similar to its non-magnetic rare-earth monopnictide counterpart LaSb [49], CeBi has a bulk anisotropic Fermi surface with elongated electron Fermi pockets [38,47].…”

“…CeBi has a rock-salt cubic crystal lattice, resulting in identical electronic structures along the kx, ky and kz directions of the Brillouin zone [47]. Similar to its non-magnetic rare-earth monopnictide counterpart LaSb [49], CeBi has a bulk anisotropic Fermi surface with elongated electron Fermi pockets [38,47]. Thus, we expect to see anisotropic MR in CeBi in a rotating magnetic field.…”