General, Strong Impurity-Strength Dependence of Quasiparticle Interference

Quasiparticle interference patterns in momentum space give rich and important information on the underlying electronic structure of surfaces and two-dimensional materials. The quasiparticle interference patterns are often compared with impurity-independent quantities, such as the joint density of states or spin-dependent scattering probability. In this presentation, we show that the quasiparticle interference pattern is strongly dependent on the strength of the impurity even in the simplest case of a single-site impurity on the square lattice with an s orbital per site. We analyze this pattern by decomposing the pattern into an impurity-dependent T-matrix and a momentum-dependent part, the product of two Green functions. Then, we show the results of our T-matrix analysis on TaAs, an archetype Weyl semimetal, obtained with first-principles calculations. The results show very rich, impurity-dependent quasiparticle interference patterns. Thus, our study demonstrates that quasiparticle-interference patterns should be analyzed using the information on the type of impurities.