Figure 5
Comparison of excitonic insulators with superconductors. (A) The densities of states (DOS’s) of normal metal (NM) and superconductor (SC). (B) The corresponding optical conductivities (σ1(ω)). The thick red vertical arrow indicates the superfluid spectral weight condensed at zero frequency. (C) The accumulated spectral weights (SW(ω)) of NM and SC. (D) The differential spectral weight (ΔSW(ω)) between NM and SC. (E) DOS’s of zero-gap semiconductor (ZGSC) and excitonic insulator (EI); the red (electrons) and blue (holes) dashed horizontal lines show the thermal excitations, (F) σ1(ω); the black (for ZGSC) and red (for EI), (G) SW(ω), and (H) ΔSW(ω). The red arrow shows the missing (or superfluid) spectral weight, which is closely related to the excitonic superfluid plasma frequency.
