Signatures of two- and three-dimensional semimetals from circular dichroism

Abstract

Topological invariants are crucial quantities for classifying materials with topological phases. Hence, their connections with experimentally measurable quantities are extremely important. In this context, circular dichroism (CD) provides a protocol to detect the Chern number C0 of the lowest energy Bloch band (LBB) of a semimetal. This hinges on the unequal depletion rates of the Bloch electrons from a filled LBB, under the action of a time-periodic circular drive, depending on the chirality of the polarization. According to the dimensionality of the system (i.e., whether it is two-or three-dimensional), the integrated differential rate for depletion has to be formulated a bit differently in order to relate it to C0. Our aim is to capture the nature of the CD response for semimetals with anisotropic band dispersions. We show that while the quantization of the CD response for the three-dimensional cases is strongly sensitive to anisotropy, the two-dimensional counterparts show a perfectly quantized response.

Direction-dependent conductivity in planar Hall set-ups with tilted Weyl/multi-Weyl semimetals

“…Other smokinggun signatures of nontrivial topology in bandstructures, studied widely in the literature, include intrinsic anomalous Hall effect [35][36][37], planar thermal Hall 3 PHE is also observed in ferromagnets, but its value is very small. effect [23,[29][30][31][32][38][39][40][41], magneto-optical conductivity when Landau levels need to be considered [42][43][44], Magnus Hall effect [45][46][47], circular dichroism [48,49], circular photogalvanic effect [50][51][52][53], and transmission of quasiparticles across potential barriers/wells [54][55][56][57].…”

Direction-dependent conductivity in planar Hall set-ups with tilted Weyl/multi-Weyl semimetals

“…The chiral anomaly leads to another effect in topological nodal phases, namely the giant planar Hall effect (PHE) [29][30][31][32][33][34], which is the appearance of a large transverse voltage when B is not aligned along E. Observation of the negative LMR and the PHE, with a specific dependence of the conductivity/resistivity tensors on the angle θ between E and B (obtained theoretically from the semiclassical Boltzmann formalism), constitutes a telltale evidence for the chiral anomaly. 1 Other smoking-gun signatures of nontrivial topology in bandstructures, studied widely in the literature, include intrinsic anomalous Hall effect [35][36][37], planar thermal Hall effect [23,[29][30][31][32][38][39][40][41], magneto-optical conductivity when Landau levels need to be considered [42][43][44], Magnus Hall effect [45][46][47], circular dichroism [48,49], circular photogalvanic effect [50][51][52][53], and transmission of quasiparticles across potential barriers/wells [54][55][56][57].…”