Intriguing electronic and optical prospects of FCC bimetallic two-dimensional heterostructures: epsilon near-zero behaviour in UV-vis range

Abstract

Higher superconducting critical temperature and large-area epsilon-near-zero interfaces are two long-standing goals of Condensed Matter Physics and Optics. Motivated by the recent advancements of experimental interests on metallic nanostructures, we have theoretically investigated some selected bimetallic FCC combinations starting from large-area interface to embedded and doped two-dimensional (2D) nanostructures. Using different first-principles techniques, encompassing density functional theory (DFT), time-dependent DFT (TDDFT), phonon and DFT-coupled quantum transport, we propose the prospects of some selective bimetallic nanostructures like Au/Ag and Pt/Pd to exhibit exotic electronic phenomena. For 2D doped and embedded nanostructures of these systems, non-trivial band-structure and Fermi-surface topology may be emblematic to the presence of instabilities like charge density waves. We specifically highlight the optical attributes extracted from the TDDFT calculations for these systems, where interfacial morphology induced band-localization leads to near-zero behavior of both real and imaginary parts of the dynamical dielectric response is observed in the ultra-violet to visible (UV-vis) optical range. Low-energy intra-band plasmonic oscillations present for individual metallic surfaces are completely suppressed for embedded and doped nanostructures. Phonon-dispersion of the model systems indicates the presence of soft phonons and dynamical instabilities. Quantum transport calculations on simplest possible device made out of these bimetallic systems reveals generation of highly transmitting pockets over the cross-sectional area for some selected device geometry. We envisage that, if observed experimentally, such systems may lead to many fascinating physics and applications in many diverse fields ranging from condensed matter physics to optics or even more.