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HL: Fachverband Halbleiterphysik

HL 8: Ultrafast Phenomena I

HL 8.4: Vortrag

Montag, 18. März 2024, 15:45–16:00, EW 015

Photoinduced charge density waves in transition metal dichalcogenides — •Kris Holtgrewe, Giovanni Marini, and Matteo Calandra Buonaura — University of Trento, Italy

Phase transitions induced by ultrafast photoexcitation are an active area of research for materials whose properties can be tuned by light. Transition metal dichalcogenides (TMDs) are a promising class of such materials. Previous studies have demonstrated that photoexcited single layers of MoTe₂ and WTe₂ show charge density wave (CDW) orders which can be controlled by the photoexcitation strength [1].

In this work, we investigate whether similar phase transitions occur in other 2D TMD homologues, namely MoS₂, WS₂, MoSe₂, and WSe₂. Using constrained density functional theory (cDFT) [2], we infer supercell reconstructions from the unstable phonon dispersions of the photoexcited TMDs and analyse their impact on the electronic properties. Our findings reveal that all TMDs undergo a similar CDW-like structural distortion at a material-dependent critical photoexcitation strength. This distortion is characterised by the formation of metal-metal bonds, driven by a charge redistribution between the d orbitals of the metal atoms. Our results provide a comprehensive understanding of the underlying microscopic processes and pave the way for a general strategy to identify further candidates for photoinduced phase transitions.

[1] G Marini et al. Phys. Rev. Lett. 127, 257401 (2021)

[2] G Marini et al. Phys. Rev. B 104, 144103 (2021)

Keywords: transition metal dichalcogenides; non-equilibrium dynamics; charge density wave; density functional theory; ultrafast phase transitions