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At a temperature of 200K, the quasi-two-dimensional system 1T-TiSe2 undergoes a phase transition towards a charge density wave (CDW) phase, which is accompanied by a periodic lattice distortion (PLD). We propose the exciton condensate phase as the purely electronic origin of the CDW phase of 1T-TiSe2. Measured angle-resolved photoemission spectroscopy data are compared with photoemission intensity maps generated by the spectral function within this model. We also discuss features of the model which allow extracting from the experiment the temperature dependence of the corresponding order parameter. Finally, we show recent results on the coupling of the exciton condensate to the lattice, which demonstrate that the presence of condensed excitons are capable of producing the observed PLD. |
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