Vibrational Dichroism of Chiral Valley Phonons

Pan, Yiming; Caruso, Fabio

doi:10.1021/acs.nanolett.3c01904

Cited by 6 publications

(3 citation statements)

References 68 publications

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“…A thorough understanding of ultrafast excited carrier dynamics is crucial for optoelectronic devices, − quantum materials, − and other materials science. − Charge carrier dynamics encompass a myriad of complex processes, pushing the boundaries of both experimental and theoretical research tools. , The emergence of sophisticated experimental methods in the ultrafast dynamics domain, ,− i.e., ultrafast time- and angle-resolved photoemission spectroscopy (TR-ARPES), ,− offers an accurate mapping of band structures, providing in-depth energy and momentum data while tracking electron activity at a femtosecond time scale. However, there is still a significant gap in the development of comparable theoretical tools, especially for first-principles approaches.…”

Section: Introductionmentioning

confidence: 99%

Nonadiabatic Molecular Dynamics with Non-Condon Effect of Charge Carrier Dynamics

Lu,

Long

2023

J. Am. Chem. Soc.

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Nonradiative multiphonon transitions play a crucial role in understanding charge carrier dynamics. To capture the non-Condon effect in nonadiabatic molecular dynamics (NA-MD), we develop a simple and accurate method to calculate noncrossing and crossing k-point NA coupling in momentum space on an equal footing and implement it with a trajectory surface hopping algorithm. Multiple k-point MD trajectories can provide sufficient nonzero momentum multiphonons coupled to electrons, and the momentum conservation is maintained during nonvertical electron transition. The simulations of indirect bandgap transition in silicon and intra-and intervalley transitions in graphene show that incorporation of the non-Condon effect is needed to correctly depict these types of charge dynamics. In particular, a hidden process is responsible for the delayed nonradiative electron−hole recombination in silicon: the thermal-assisted rapid trapping of an excited electron at the conduction band minimum by a long-lived higher energy state through a nonvertical transition extends charge carrier lifetime, approaching 1 ns, which is about 1.5 times slower than the direct bandgap recombination. For graphene, intervalley scattering takes place within about 225 fs, which can occur only when the intravalley relaxation proceeds to about 50 fs to gain enough phonon momentum. The intra-and intervalley scattering constitute energy relaxation, which completes within sub-500 fs. All the simulated time scales are in excellent agreement with experiments. The study establishes the underlying mechanisms for a long-lived charge carrier in silicon and valley scattering in graphene and underscores the robustness of the non-Condon approximation NA-MD method, which is suitable for rigid, soft, and large defective systems.

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Section: Introductionmentioning

confidence: 99%

Nonadiabatic Molecular Dynamics with Non-Condon Effect of Charge Carrier Dynamics

Lu,

Long

2023

J. Am. Chem. Soc.

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“…Both findings highlight the importance of a combined approach involving methods sensitive to lattice as well as electronic degrees of freedom, allowing a comprehensive picture of thermalization in anisotropic materials. Given its surface sensitivity, ultrafast low-energy electron scattering represents a suitable probe to study the dynamics of surface-bound phonons 57 , chiral phonons 58 – 60 and structural non-equilibrium associated with phonon-mediated charge transfer in heterostructures and moiré superlattices 24 .…”

Section: Discussionmentioning

confidence: 99%

Non-thermal phonon dynamics and a quenched exciton condensate probed by surface-sensitive electron diffraction

Kurtz,

Dauwe,

Yalunin

et al. 2024

Nat. Mater.

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Interactions among and between electrons and phonons steer the energy flow in photo-excited materials and govern the emergence of correlated phases. The strength of electron–phonon interactions, decay channels of strongly coupled modes and the evolution of three-dimensional order are revealed by electron or X-ray pulses tracking non-equilibrium structural dynamics. Despite such capabilities, the growing relevance of inherently anisotropic two-dimensional materials and functional heterostructures still calls for techniques with monolayer sensitivity and, specifically, access to out-of-plane phonon polarizations. Here, we resolve non-equilibrium phonon dynamics and quantify the excitonic contribution to the structural order parameter in 1T-TiSe2. To this end, we introduce ultrafast low-energy electron diffuse scattering and trace strongly momentum- and fluence-dependent phonon populations. Mediated by phonon–phonon scattering, a few-picosecond build-up near the zone boundary precedes a far slower generation of zone-centre acoustic modes. These weakly coupled phonons are shown to substantially delay overall equilibration in layered materials. Moreover, we record the surface structural response to a quench of the material’s widely investigated exciton condensate, identifying an approximate 30:70 ratio of excitonic versus Peierls contributions to the total lattice distortion in the charge density wave phase. The surface-sensitive approach complements the ultrafast structural toolbox and may further elucidate the impact of phonon scattering in numerous other phenomena within two-dimensional materials, such as the formation of interlayer excitons in twisted bilayers.

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“…In this process, chiral phonons carrying PAM participate in the intervalley transition of electrons. As an ideal platform for chiral phonon research, many novel effects and phenomena related to chiral phonons in two-dimensional (2D) TMD materials have been discovered, such as entanglement of single photons and chiral phonons, brightening of the momentum-dark intervalley excitons, − nonlinear valley phonon scattering, vibrational dichroism of chiral valley phonons, etc. If the chirality of phonons can be manipulated in these TMD materials, it will have an important significance and impact on the study of chiral phonons and other related fields.…”

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confidence: 99%

Phonon Chirality Manipulation Mechanism in Transition-Metal Dichalcogenide Interlayer-Sliding Ferroelectrics

Chen,

Wang,

Feng

et al. 2023

Nano Lett.

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As an ideal platform, both the theoretical prediction and first experimental verification of chiral phonons are based on transition-metal dichalcogenide materials. The manipulation of phonon chirality in these materials will have a profound effect on the study of chiral phonons. In this work, we utilize the sliding ferroelectric effect to realize the phonon chirality manipulation mechanism in transition-metal dichalcogenide materials. Based on first-principles calculations, we find the different manipulation effects of interlayer sliding on the phonon chirality and Berry curvature in bilayer and four-layer MoS2 sliding ferroelectrics. These further affect the phonon angular momentum and magnetization under a temperature gradient and the phonon Hall effect under a magnetic field. Our work connects two emerging fields and opens up a new route to manipulating phonon chirality in transition-metal dichalcogenide materials through the sliding ferroelectric mechanism.

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Vibrational Dichroism of Chiral Valley Phonons

Cited by 6 publications

References 68 publications

Nonadiabatic Molecular Dynamics with Non-Condon Effect of Charge Carrier Dynamics

Nonadiabatic Molecular Dynamics with Non-Condon Effect of Charge Carrier Dynamics

Non-thermal phonon dynamics and a quenched exciton condensate probed by surface-sensitive electron diffraction

Phonon Chirality Manipulation Mechanism in Transition-Metal Dichalcogenide Interlayer-Sliding Ferroelectrics

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