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Existence of short-range excitonic correlations above Tc in 1T-TiSe2

Determine whether short-range excitonic correlations persist in 1T-TiSe2 above the charge-density-wave transition temperature, distinguishing excitonic fluctuations from short-range lattice (phonon) fluctuations known to occur in the normal state.

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Background

In the normal state of 1T-TiSe2, thermal diffuse scattering indicates short-range lattice fluctuations associated with incipient CDW order. A key unresolved issue is whether short-range excitonic correlations also exist above Tc, which would support an excitonic character of the ground state in a quasi-2D system where fluctuations are prevalent, and whether such correlations can be disentangled from phonon-driven effects in equilibrium measurements.

References

Specifically, while mounting evidence such as thermal diffuse scattering in X-ray and electron diffractions has pointed out the presence of short-range lattice fluctuations, it remains to be seen whether short-range excitonic correlations are also present above T_c, which constitute a necessary condition for the excitonic character of the ground state in this quasi-2D system.

— 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 Section: Persistent excitonic fluctuations in the normal state