Tracking the catastrophic collapse of hybrid exciton-phonon order in a quantum material

Omar Abdul-Aziz; Danilo Comini; Johannes Lang; Nils Bartel; Michael Buchhold; Sebastian Diehl; Daniel Wolverson; Charles J. Sayers; Giulio Cerullo; Paul H.M. van Loosdrecht; Hamoon Hedayat

doi:10.1038/s41467-026-75887-9

Tracking the catastrophic collapse of hybrid exciton-phonon order in a quantum material

Omar Abdul-Aziz
, Danilo Comini
, Johannes Lang
, Nils Bartel
, Michael Buchhold
, Sebastian Diehl
, Daniel Wolverson
, Charles J. Sayers
, Giulio Cerullo
, Paul H.M. van Loosdrecht
, Hamoon Hedayat

University of Cologne
University of Innsbruck
Politecnico di Milano
IFN-CNR

Research output: Contribution to journal › Article › peer-review

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-TiSe₂, 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.

Original language	English
Article number	7607
Number of pages	11
Journal	Nature Communications
Volume	17
Issue number	1
Early online date	30 Jul 2026
DOIs	https://doi.org/10.1038/s41467-026-75887-9
Publication status	E-pub ahead of print - 30 Jul 2026

Bibliographical note

Publisher Copyright:
© The Author(s) 2026.

Data Availability Statement

The source data supporting the main and Supplementary Figs. are available in Zenodo at https://doi.org/10.5281/zenodo.20395573. The repository includes a README file mapping each figure panel to the corresponding data files.

Acknowledgements

The authors acknowledge financial support from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through CRC 1238 (Project No. 277146847, Control and Dynamics of Quantum Materials). Computational work was performed on the University of Bath’s High Performance Computing Facility, supported by the EU Horizon 2020 OCRE/GEANT project “Cloud funding for research”. G.C. acknowledges financial support from the European Union’s NextGenerationEU Programme via the I-PHOQS Infrastructure (IR0000016, ID D2B8D520, CUP B53C22001750006, “Integrated infrastructure initiative in Photonic and Quantum Sciences”). C.J.S. and G.C. acknowledge support from the Horizon Europe EIC Pathfinder Open program under grant agreement No. 101130384 (QUONDENSATE). Open Access funding enabled and organized by Projekt DEAL.

Funding

The authors acknowledge financial support from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through CRC 1238 (Project No. 277146847, Control and Dynamics of Quantum Materials). Computational work was performed on the University of Bath’s High Performance Computing Facility, supported by the EU Horizon 2020 OCRE/GEANT project “Cloud funding for research”. G.C. acknowledges financial support from the European Union’s NextGenerationEU Programme via the I-PHOQS Infrastructure (IR0000016, ID D2B8D520, CUP B53C22001750006, “Integrated infrastructure initiative in Photonic and Quantum Sciences”). C.J.S. and G.C. acknowledge support from the Horizon Europe EIC Pathfinder Open program under grant agreement No. 101130384 (QUONDENSATE). Open Access funding enabled and organized by Projekt DEAL.

Funders	Funder number
Projekt DEAL
GEANT project “Cloud funding for research”
EU Horizon 2020 OCRE
Deutsche Forschungsgemeinschaft	277146847, CRC 1238
Horizon Europe EIC Pathfinder Open program	101130384
European Commission	ID D2B8D520, CUP B53C22001750006, IR0000016

ASJC Scopus subject areas

General Chemistry
General Biochemistry,Genetics and Molecular Biology
General
General Physics and Astronomy

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10.1038/s41467-026-75887-9Licence: CC BY

Cite this

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title = "Tracking the catastrophic collapse of hybrid exciton-phonon order in a quantum material",

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-TiSe2, 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 (\textasciitilde{}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.",

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AU - Buchhold, Michael

AU - Diehl, Sebastian

AU - Wolverson, Daniel

AU - Sayers, Charles J.

AU - Cerullo, Giulio

AU - van Loosdrecht, Paul H.M.

AU - Hedayat, Hamoon

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Tracking the catastrophic collapse of hybrid exciton-phonon order in a quantum material

Abstract

Bibliographical note

Data Availability Statement

Acknowledgements

Funding

ASJC Scopus subject areas

Access to Document

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