# Large optical conductivity of Dirac semimetal Fermi arc surfaces states

## TL;DR

This paper reveals that Fermi arc surface states in Dirac semimetals exhibit a large, anisotropic optical conductivity, offering a new way to probe their topological surface states through optical methods.

## Contribution

It demonstrates the strong, anisotropic light-matter interaction of Fermi arc carriers and links the large optical conductivity to the separation of Dirac nodes, providing novel insights into topological surface states.

## Key findings

- Fermi arc carriers have a large, anisotropic optical conductivity.
- Optical conductivity is maximized when light is polarized transverse to Fermi arcs.
- Large conductivity persists with doping, linked to Dirac node separation.

## Abstract

Fermi arc surface states, a hallmark of topological Dirac semimetals, can host carriers that exhibit unusual dynamics distinct from that of their parent bulk. Here we find that Fermi arc carriers in intrinsic Dirac semimetals possess a strong and anisotropic light matter interaction. This is characterized by a large Fermi arc optical conductivity when light is polarized transverse to the Fermi arc; when light is polarized along the Fermi arc, Fermi arc optical conductivity is significantly muted. The large surface spectral weight is locked to the wide separation between Dirac nodes and persists as a large Drude weight of Fermi arc carriers when the system is doped. As a result, large and anisotropic Fermi arc conductivity provides a novel means of optically interrogating the topological surfaces states of Dirac semimetals.