Coupled plasmon-LO-phonon modes in the ground state of a GaAs-based electron-electron biwire system

Abstract

We study the coupled plasmon-longitudinal optical-phonon (pl-LO-ph) modes in a GaAs-based electron-electron (e-e) biwire system at absolute zero within the dynamic mean-field approximation of Singwi and others (popularly known as the qSTLS theory). Here, in addition to the standard electron-electron (e-e) interactions, we also take into account the electron-phonon (e-ph) coupling and calculate pl-LO-ph modes at some selected values of wire-width, inter-wire separation and electron number density. The coupled modes are found to resonantly split into eight branches, four of which lie outside and four inside the electron-hole (e-h) pair continuum. Out of four branches which exist above the e-h pair continuum, two are plasmon-like modes having energies below than that of transverse optical (TO) phonons, and the other two are phonon-like modes having energies above longitudinal optical (LO) phonons. Additionally, we compare the plasmon-like modes with true plasmons (resulting only from the typical e-e interactions) and note that the e-ph coupling softens the true plasmon modes.