Anisotropic plasmons, Friedel oscillations, and screening in 8-Pmmn borophene
Abstract8-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.