Effect of disorder on density of states and conductivity in higher-order Van Hove singularities in two-dimensional bands

We study systems with energy bands in two dimensions, hosting higher order Van Hove singularities (HOVHS) in the presence of disorder, using standard diagrammatic techniques for impurity averaging. In the clean limit, such singularities cause power-law divergence in the density of states (DOS), and this is expected to strongly affect electronic correlation. In order to analyze the signatures of these singularities in disordered systems, we employ various Born approximations, culminating in the self-consistent (non) Born approximation. Although the divergence of the DOS is smeared, we find that the shape of the DOS, as characterized by the power-law tail and the universal ratio of prefactors, is retained slightly away from the singularity. This could help us to understand current and future experiments on materials that can be tuned to host HOVHS. The impurity-induced smearing is calculated and analyzed for several test cases of singularities. We also study the effects of impurities on electrical conductivity and determine the regimes where the quantitative features of the power-law DOS manifest in the conductivity.

Automated summary

This study investigates the effect of disorder on systems with energy bands in two dimensions that have higher order Van Hove singularities (HOVHS). The authors utilize standard diagrammatic techniques for impurity averaging and analyze the signatures of these singularities in disordered systems. They find that while the divergence of the density of states (DOS) is smeared, the shape of the DOS is retained slightly away from the singularity, which may help understand experiments on materials that can host HOVHS. The impurity-induced smearing is calculated and the effects on electrical conductivity are studied.