Electron- hole fluctuation phase in 1T-TiSe2

To address the fluctuation regime above the critical temperature of the charge-density-wave phase of 1T-TiSe2, we perform calculations using the Bethe-Salpeter equation for treating strong electron-hole correlations. Calculated photoemission intensity maps are in good agreement with the measured ones and provide a deeper understanding of the phase transition in terms of an electronic instability. We find that no real nesting of the Fermi surface is necessary, but crossing points between different Fermi surface sheets produce an instability with a wave vector corresponding to the commensurate charge distribution observed below the critical temperature. Finally, we also consider the effect of the electron-phonon interaction on the calculated spectra to discriminate what mechanism is responsible for the instability and conclude that the electron-hole fluctuation scenario is more likely to occur.