# Anisotropic plasmons, Friedel oscillations and dynamical screening in $8-Pmmn$ borophene

## TL;DR

This paper analytically investigates the anisotropic plasmon modes, Friedel oscillations, and screening properties of $8-Pmmn$ borophene, revealing undamped plasmon modes and anisotropic decay patterns in oscillations.

## Contribution

It provides the first analytical calculation of the density-density response function and explores the anisotropic plasmon dispersion and Friedel oscillations in $8-Pmmn$ borophene.

## Key findings

- Anisotropic plasmon mode remains undamped at higher energies along mirror symmetry.
- Friedel oscillations decay as $r^{-3}$ with anisotropic amplitude and periodicity.
- Screening properties are direction-dependent due to anisotropic Dirac cone.

## Abstract

$8-Pmmn$ borophene is a polymorph of borophene which hosts an anisotropic tilted Dirac cone. Using a low energy effective Hamiltonian for borophene, we analytically calculate the density-density response function of borophene and study its anisotropic plasmon dispersion and screening properties. We find that the anisotropic plasmon mode in $8-Pmmn$ borophene, remains undamped for higher energies along the mirror symmetry direction. The friedel oscillation in borophene is found to decay as $r^{-3}$ in the large $r$ limit, with both the amplitude as well as the periodicity of the Friedel oscillations being anisotropic.