Mapping the nonequilibrium order parameter of a quasi-two dimensional charge density wave system

Sayers, C. J.; Zhang, Y.; Sanders, C. E.; Chapman, R. T.; Wyatt, A. S.; Chatterjee, G.; Springate, E.; Cerullo, G.; Wolverson, D.; Da Como, E.; Carpene, E.

doi:10.1038/s42005-024-01879-0

DOE OSTI · 2583231

Mapping the nonequilibrium order parameter of a quasi-two dimensional charge density wave system

Sayers, C. J.·Zhang, Y.·Sanders, C. E.·Chapman, R. T.·Wyatt, A. S.·Chatterjee, G.·Springate, E.·Cerullo, G.·Wolverson, D.·Da Como, E.·Carpene, E.

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Abstract

The driving force of a charge density wave (CDW) transition in quasi-two dimensional systems is still debated, while being crucial in understanding electronic correlation in such materials. Here we use femtosecond time- and angle-resolved photoemission spectroscopy combined with computational methods to investigate the coherent lattice dynamics of a prototypical CDW system. The photo-induced temporal evolution of the periodic lattice distortion associated with the amplitude mode reveals the dynamics of the free energy functional governing the order parameter. Our approach establishes that optically-induced screening rather than CDW melting at the electronic level leads to a transiently modified potential which explains the anharmonic behaviour of the amplitude mode and discloses the structural origin of the symmetry-breaking phase transition.

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Sayers, C. J., Zhang, Y., Sanders, C. E., Chapman, R. T., Wyatt, A. S., Chatterjee, G., Springate, E., Cerullo, G., Wolverson, D., Da Como, E., Carpene, E.. 2024-11-28. Mapping the nonequilibrium order parameter of a quasi-two dimensional charge density wave system. https://doi.org/10.1038/s42005-024-01879-0

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