Carta Acesso aberto Revisado por pares

Non-thermal separation of electronic and structural orders in a persisting charge density wave

2014; Nature Portfolio; Volume: 13; Issue: 9 Linguagem: Inglês

10.1038/nmat4042

ISSN

1476-4660

Autores

M. Porer, U. Leierseder, Jean‐Michel Ménard, Hatem Dachraoui, Leonidas Mouchliadis, I. E. Perakis, U. Heinzmann, J. Demšar, Kai Roßnagel, R. Huber,

Tópico(s)

Organic and Molecular Conductors Research

Resumo

The electronic and structural components of charge density waves occurring in layered transition metal dichalcogenides are known to be interdependent, yet have only been probed in separate measurements. Now, a broadband terahertz spectroscopy approach that monitors the evolution of these two order parameters simultaneously is demonstrated. The simultaneous ordering of different degrees of freedom in complex materials undergoing spontaneous symmetry-breaking transitions often involves intricate couplings that have remained elusive in phenomena as wide ranging as stripe formation1, unconventional superconductivity1,2,3,4,5,6,7 or colossal magnetoresistance1,8. Ultrafast optical, X-ray and electron pulses can elucidate the microscopic interplay between these orders by probing the electronic and lattice dynamics separately9,10,11,12,13,14,15,16,17, but a simultaneous direct observation of multiple orders on the femtosecond scale has been challenging. Here we show that ultrabroadband terahertz pulses can simultaneously trace the ultrafast evolution of coexisting lattice and electronic orders. For the example of a charge density wave (CDW) in 1T-TiSe2, we demonstrate that two components of the CDW order parameter—excitonic correlations and a periodic lattice distortion (PLD)—respond very differently to 12-fs optical excitation. Even when the excitonic order of the CDW is quenched, the PLD can persist in a coherently excited state. This observation proves that excitonic correlations are not the sole driving force of the CDW transition in 1T-TiSe2, and exemplifies the sort of profound insight that disentangling strongly coupled components of order parameters in the time domain may provide for the understanding of a broad class of phase transitions.

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