Structurally assisted melting of excitonic correlations in 1T-TiSe2

Abstract

The simultaneous condensation of electronic and structural degrees of freedom gives rise to new states of matter, including superconductivity and charge-density-wave formation. When exciting such a condensed system, it is commonly assumed that the ultrafast laser pulse disturbs primarily the electronic order, which in turn destabilizes the atomic structure. Contrary to this conception, we show here that structural destabilization of few atoms causes melting of the macroscopic ordered charge-density wave in 1T-TiSe2. Using ultrafast pump-probe non-resonant and resonant X-ray diffraction, we observe full suppression of the Se 4p orbital order and the atomic structure at excitation energies more than one order of magnitude below the suggested excitonic binding energy. Complete melting of the charge-density wave occurs 4-5 times faster than expected from a purely electronic charge-screening process, strongly suggesting a structurally assisted breakup of excitonic correlations. Our experimental data clarifies several questions on the intricate coupling between structural and electronic order in stabilizing the charge-density-wave in 1T-TiSe2. The results further show that electron-phonon-coupling can lead to different, energy dependent phase-transition pathways in condensed matter systems, opening new possibilities in the conception of non-equilibrium phenomena at the ultrafast scale.

arXiv comment19 pages, 4 figures

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• A New Era of Excitonic Insulators
• Investigation of the Non-equilibrium State of Strongly Correlated Materials by Complementary Ultrafast Spectroscopy Techniques
• Electron correlations rule the phonon-driven instability in single layer TiSe${}_2$
• Ultrafast Control of Crystal Structure in a Topological Charge-Density-Wave Material
• Carrier-Density Control of the Quantum-Confined 1$T$-TiSe${}_2$ Charge-Density-Wave
• In-plane anisotropy of charge density wave fluctuations in 1$T$-TiSe${}_2$
• Photo-induced Dynamics and Momentum Distribution of Chiral Charge Density Waves in 1T-TiSe${}_2$
• Optical amplification in a CDW-phase of a quasi-two dimensional material
• Melting of magnetic order in ${\mathrm{NaOsO}}_3$ by fs laser pulses
• Time-Resolved Photoemission Spectroscopy of Quantum Materials Using High Harmonic Generation: Probing Electron-Phonon Interactions and Non-Equilibrium Dynamics
• Revisiting the charge-density-wave superlattice of 1$T$-TiSe${}_2$