Excitonic resonances in the 2D extended Falicov-Kimball model

¹ Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald - D-17489 Greifswald, Germany, EU
² School of Physics, University of New South Wales - Kensington 2052, Sydney NSW, Australia
³ Institut für Theoretische Physik, Technische Universität Dresden - D-01062 Dresden, Germany, EU

^a holger.fehske@physik.uni-greifswald.de

Received: 27 January 2011
Accepted: 15 May 2011

Abstract

Using the projector-based renormalization method we investigate the formation of the excitonic insulator phase in the two-dimensional (2D) spinless Falicov-Kimball model with dispersive f electrons and address the existence of excitonic bound states at high temperatures on the semiconductor side of the semimetal-semiconductor transition. To this end we calculate the imaginary part of the dynamical electron-hole pair susceptibility and analyze the wave vector and energy dependence of excitonic resonances emerging in the band gap. We thereby confirm the existence of the exciton insulator and its exciton environment within a generic two-band lattice model with local Coulomb attraction.