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Mechanistic role of excitonic correlations in driving the CDW transition in 1T-TiSe2

Ascertain whether excitonic correlations drive the charge-density-wave transition in 1T-TiSe2 and determine the mechanism by which excitonic correlations lead to the formation of the 2×2×2 superlattice at the transition temperature near 200 K.

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Background

The quasi-2D material 1T-TiSe2 exhibits a CDW transition to a 2×2×2 superlattice that has been hypothesized to involve exciton condensation. However, equilibrium measurements have offered conflicting evidence, and interpretations of collective excitations attributed to exciton condensation have been challenged. Resolving whether and how excitonic correlations contribute causally to the CDW transition, and disentangling them from lattice (phonon) effects, remains a central problem.

References

Despite decades of close scrutiny, whether and how excitonic correlations drive the CDW transition remains under debate, and one of the most convincing pieces of evidence so far that reports on the collective excitation of the exciton condensation has recently come into question.

— Core-level signature of long-range density-wave order and short-range excitonic correlations probed by attosecond broadband spectroscopy (2407.00772 - Zong et al., 30 Jun 2024) in Introduction