# Rashba Metamaterials and Metasurfaces with Zero Reflectivity and Effect of Surface States in Ultrathin Metal Films

## TL;DR

Researchers show how ultrathin metal films can create surfaces with zero reflectivity, opening new possibilities for optical technologies.

## Contribution

The discovery of Rashba metamaterials with zero reflectivity using ultrathin metal films on oxide layers.

## Key findings

- Ultrathin metal films on oxide layers can achieve zero reflectivity due to surface states.
- Rashba metamaterials can be tuned to function as high-resolution Veselago lenses.
- The effect was demonstrated with multiple metals and semimetals at varying thicknesses.

## Abstract

Metals, renowned
for their high reflectivity, find extensive
use
in various technological applications, from mirrors to optical coatings
in radars, telescopes, and mobile communications. However, their potential
in antireflective coatings has remained largely untapped. In this
study, we demonstrate that by applying an ultrathin metallic film
onto an oxide layer, we can achieve a flawless optical surface with
zero reflectivity. This phenomenon has been successfully observed
across various metals, including Sn, Ag, Au, Pt, Bi, and Nb, showcasing
its broad applicability. The underlying principle lies in the emergence
of surface states, where the Rashba effect is strong, which give rise
to the formation of Rashba metamaterial and metasurface (RMM) structures.
Remarkably, these RMMs can be fine-tuned to act as high-resolution
Veselago lenses. To illustrate, we achieved zero reflectivity with
an RMM consisting of a 1 nm thick Sn metal film on a 1 nm Ge buffer,
situated on a 60 nm Al2O3/Si substrate. Similar
results were observed for other metals (Pt, Au, Ag, and Nb) and semimetals
(Bi) by adjusting the film thickness to 2, 3, 5, 10, and 6 nm, respectively.
The revelation of RMMs with zero reflectivity (R =
0) has tremendous potential to revolutionize optical device technologies,
covering renewable energy, optoelectronics, and the telecommunications
industry.