Speaker
Description
Weyl nodal loop semimetals are topological semimetals where the valence and conduction bands linearly touch along one dimensional loops in momentum space. A manifestation of their non-trivial topology is the presence of zero energy surface states, induced by chiral symmetry, on surfaces parallel to the loop plane. Unlike their insulator counterparts, these exotic phases may be unstable to small perturbations that respect their topology-protecting symmetries. Results for symmetry-breaking disorder have been reported. However, the case of vacancies preserves the underlying symmetry, and remains largely open.
Here, we will discuss the effects of vacancies in the bulk of a nodal loop semimetal tight-binding model, as well as an effective low energy model for a circular nodal loop, where an analytical approach is tractable. We focus on the changes in the density of states (DOS), computed via a projected Green’s function formalism, and study the linear optical conductivity in the presence of vacancies. A single cell-vacancy creates broad peaks near the Fermi level, but the system remains a semimetal, whereas site-vacancies induce a sharp peak at zero energy.
The optical conductivity in the presence of site vacancies has a sharp absorption edge at $\omega=E_F$, followed by a power law decay which, for a single vacancy, goes as $\sim 1/\omega^2$. The cell vacancy case reveals a complete vanishing of the optical gap.
| Which topic best fits your talk? | Condensed Matter Physics and Nanomaterials |
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