Ultrafast dynamics of hot carriers in a quasi–two-dimensional electron gas on InSe

Chen, Zhe‐Sheng; Sjakste, Jelena; Dong, Jinwei; Taleb‐Ibrahimi, A.; Rueff, Jean‐Pascal; Shukla, Abhay; Peretti, J.; Papalazarou, E.; Marsi, M.; Perfetti, L.

doi:10.1073/pnas.2008282117

Cited by 14 publications

(12 citation statements)

References 43 publications

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“…5,13,16,[21][22][23] Time-and angle-resolved photoemission spectroscopy (tr-ARPES) has led the way in the experimental investigation of the out-ofequilibrium carrier dynamic in TMDs, 24 providing direct insight on the influence of electronphonon interactions on the carrier dynamics. 25 Information regarding the lattice and its nonequilibrium dynamics, however, can only be inferred indirectly from its effects on the electrons, as, e.g., transient changes of the Fermi level, electron binding energies, or quasiparticle linewidths. 15,16,26 Femtosecond electron diffuse scattering 27 (FEDS) probes the progressive change of phonon population as the dynamics of the coupled electron-phonon system evolves, 28 and it thus offer a more direct and detailed picture of the out-of-equilibrium dynamics of the lattice.…”

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confidence: 99%

Nonequilibrium Lattice Dynamics in Monolayer MoS₂

Caruso

2021

J. Phys. Chem. Lett.

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The coupled nonequilibrium dynamics of electrons and phonons in monolayer MoS 2 is investigated by combining first-principles calculations of the electron-phonon and phononphonon interaction with the time-dependent Boltzmann equation. Strict phase-space constraints in the electron-phonon scattering are found to influence profoundly the decay path of excited electrons and holes, restricting the emission of phonons to crystal momenta close to few high-symmetry points in the Brillouin zone. As a result of momentum selectivity in the phonon emission, the nonequilibrium lattice dynamics is characterized by the emergence of a highlyanisotropic population of phonons in reciprocal space, which persists for up to 10 ps until thermal equilibrium is restored by phonon-phonon scattering. Achieving control of the nonequilibrium dynamics of the lattice may provide unexplored opportunities to selectively enhance the phonon population of two-dimensional crystals and, thereby, transiently tailor electron-phonon interactions over sub-picosecond time scales.Transition-metal dichalcogenides (TMDs) exhibit strong light-matter coupling, 1 a rich photo-physics, 2 and a unique interplay of spin, 3,4 valley, 5,6 lattice, 7 and electronic 8 degrees of freedom. These characteristics, alongside with numerous possibilities to tailor screening, 9 charge-carrier density, 7 and dimensionality, 10,11 make them promising candidates for the exploration of new pathways to achieve

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confidence: 99%

Nonequilibrium Lattice Dynamics in Monolayer MoS₂

Caruso

2021

J. Phys. Chem. Lett.

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“…InSe as suggested in a recent DFT investigation 41 . Additionally, our simulation shows that the stronger in-plane plasmonic field component at 1.58 eV excitation (see Figure SI2d) couples to the in-plane E (LO) mode better than A1 (LO) mode resulting in enhanced relative intensity.…”

Section: This Is Likely Due To Hot Carrier Induced Epc Of the E (Lo) mentioning

confidence: 86%

Plasmonic Hot Electron Induced Layer Dependent Anomalous Fröhlich Interaction in InSe

Rahaman

Aslam

et al. 2021

Preprint

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InSe is one of the most promising two-dimensional (2D) materials for electronic and optoelectronic applications because of its favourable bandgap and superior electron mobility compared to other layered semiconductors. However, due to the polar nature of InSe, Fröhlich interaction plays an important role in electrical transport, which becomes more significant in reduced dimensionality. Until now, it is not yet known how the dimensionality influences the strength and nature of the Fröhlich polaronic effect in InSe. Here, we report on layer dependent anomalous Fröhlich interaction in InSe from bulk to monolayer with the aid of plasmonic hot electron doping. When excited near the localized surface plasmon resonance, plasmonic nanostructures produce highly energetic electrons (known as hot electrons), which can be captured by a semiconductor such as InSe at the interface. These electrons then couple to the polar optical phonons via the Fröhlich interaction in InSe. With the aid of the strong plasmonic field, the Fröhlich interaction enabling us to monitor the polar phonons in conventional Raman measurements. We prepared nanostructures with three different metals (Ag, Au, and Al) using nanosphere lithography on InSe to study the hot electron doping effect by means of Raman spectroscopy. A finite element method simulation was used to understand the coupling between the plasmonic nanostructures and InSe. We observed that the intensity of polar LO phonon modes initially increases gradually with decreasing layer number and then drops drastically from 7L to 6L, i.e. at the thickness where the transition from quasi-direct to indirect bandgap occurs at room temperature. Additionally, a gradual decrease of intensity of the polar modes with decreasing layer thickness below this transition point is observed, which is due to the increasing indirect bandgap nature of InSe suggesting reduced Fröhlich coupling. Our results shed light on fundamental understanding of Fröhlich interaction in InSe, which is crucial for electronic and optoelectronic applications of this promising 2D material.

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“…2 showing the coupling of the LO mode g LO (|q|) for the neutral and doped systems. It can thus be inferred that free-carrier screening of the Fröhlich EPI would enhance the mobility of GaSe in the low-doping limit, similarly to how screening affects carrier relaxation in a related material, InSe [42]. Since there are not enough intrinsic free carriers in GaSe in the low-doping regime, one would need an external source of free-carrier screening.…”

Section: Fröhlich-limited 2d Semiconductorsmentioning

confidence: 99%

“…Unless noted otherwise, the dielectric function we consider is the layer-specific one relating to GaSe. At the level of the monolayer, the long-wavelength linearized model of the dielectric function = 1 + αq, where α is the polarizability of the 2D layer [34][35][36][37], is routinely employed [34,[42][43][44][45]. It captures only the first-order term (in q) of the dielectric function, while our model goes well beyond, as shown Fig.…”

Section: Comparison With Long-wavelength Analytical Modelsmentioning

confidence: 99%

Remote free-carrier screening to boost the mobility of Fröhlich-limited two-dimensional semiconductors

Sohier

Gibertini

Verstraete

2021

Phys. Rev. Materials

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Van der Waals heterostructures provide a versatile tool to not only protect or control, but also enhance the properties of a 2D material. We use ab initio calculations and semianalytical models to find strategies which boost the mobility of a current-carrying two-dimensional (2D) semiconductor within a heterostructure. Free-carrier screening from a metallic "screener" layer remotely suppresses electron-phonon interactions in the currentcarrying layer. This concept is most effective in 2D semiconductors whose scattering is dominated by screenable electron-phonon interactions, and in particular, the Fröhlich coupling to polar-optical phonons. Such materials are common and characterized by overall low mobilities in the small doping limit and much higher ones when the 2D material is doped enough for electron-phonon interactions to be screened by its own free carriers. We use GaSe as a prototype and place it in a heterostructure with doped graphene as the "screener" layer and boron nitride as a separator. We develop an approach to determine the electrostatic response of any heterostructure by combining the responses of the individual layers computed within density functional perturbation theory. Remote screening from graphene can suppress the long-wavelength Fröhlich interaction, leading to a consistently high mobility around 500-600 cm 2 /V s for carrier densities in GaSe from 10 11 to 10 13 cm −2 . Notably, the low-doping mobility is enhanced by a factor 2.5. This remote free-carrier screening is more efficient than more conventional manipulation of the dielectric environment, and it is most effective when the separator (boron nitride) is thin.

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Ultrafast dynamics of hot carriers in a quasi–two-dimensional electron gas on InSe

Cited by 14 publications

References 43 publications

Nonequilibrium Lattice Dynamics in Monolayer MoS₂

Nonequilibrium Lattice Dynamics in Monolayer MoS₂

Plasmonic Hot Electron Induced Layer Dependent Anomalous Fröhlich Interaction in InSe

Remote free-carrier screening to boost the mobility of Fröhlich-limited two-dimensional semiconductors

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Ultrafast dynamics of hot carriers in a quasi–two-dimensional electron gas on InSe

Cited by 14 publications

References 43 publications

Nonequilibrium Lattice Dynamics in Monolayer MoS2

Nonequilibrium Lattice Dynamics in Monolayer MoS2

Plasmonic Hot Electron Induced Layer Dependent Anomalous Fröhlich Interaction in InSe

Remote free-carrier screening to boost the mobility of Fröhlich-limited two-dimensional semiconductors

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Nonequilibrium Lattice Dynamics in Monolayer MoS₂

Nonequilibrium Lattice Dynamics in Monolayer MoS₂