Tracking the catastrophic collapse of hybrid exciton-phonon order in a quantum material.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 42532985.
- Also identified by DOI 10.1038/s41467-026-75887-9 and PMC identifier 13424097.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Revealing the hidden interactions that bind electronic and lattice components of cooperative quantum order is central to sculpting new states of matter. This challenge is epitomized by the charge density wave material 1T-TiSe<sub>2</sub>, where photoexcitation disrupts its presumed hybrid exciton-phonon order: the electronic component collapses within femtoseconds, while the periodic lattice distortion persists, challenging the definition of hybrid order. Here we resolve this paradox by uncovering a low-frequency mode (~0.13 THz) that emerges only in the ordered state and signals exciton-phonon coupling. This mode is consistent with a locked phason, a collective excitation arising when excitonic and lattice degrees of freedom share a coupled potential landscape. At a critical photoexcitation threshold, the collapse of the excitonic order flattens this potential, causing the locked phason to disappear, the charge density wave phonon to selectively overheat, and the surviving lattice distortion to become a trapped non-thermal remnant.