Phonon drag thermopower and energy loss rate in single and bilayer graphene due to piezoelectric surface acoustic phonons in Bloch-Gruneisen regime

Ansari, M. Afzal

doi:10.1016/j.physe.2021.114722

Cited by 3 publications

(3 citation statements)

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“…The linear energy dispersion approximation is limited up to the electron's energy of 0.2 eV [51,52]. The matrix element of electron-phonon interaction can be written as Z αβ kq = Z (q) G αβ kk ′ in which Z (q) is the electron-phonon coupling strength and G αβ kk ′ = [1 + αβcosθ kk ′ ] /2 is the chirality factor that arises from the overlap of wave functions, α (β) = ±1 is the band index for conduction (valence) bands of the K (K ′ ) valley in the first Brillouin zone, and θ is the angle between scattering in and out wave vectors k and k ′ [23,[31][32][33]47]. The phonons with long wavelength couple to electrons via the scalar deformation potential coupling related to the change in lattice volume or diagonal part in sublattice indices in the effective Hamiltonian [31].…”

Section: Brief Formalism and Analytical Resultsmentioning

confidence: 99%

“…In low dimensional sp 2 hybridized materials like graphene and silicene, phonon scattering is essential for the knowledge of carrier transport phenomena that anticipate the amplification of thermopower. The S p has been investigated a lot in graphene samples [19,22,26,[30][31][32] but remains untouched in silicene so far.…”

Section: Analytical Model For the Phonon Drag Thermopowermentioning

confidence: 99%

“…This area of study has been a significant focus, both theoretically and experimentally. The electron-phonon interaction in single and bilayer graphene has been extensively investigated [20][21][22][23][24][25][26][27][28][29][30][31][32][33] and has proven useful in the fabrication of devices using twodimensional materials on suitable substrates [34][35][36][37][38][39][40][41][42][43]. In the absence of extrinsic sources of scattering, such as impurities, defects, interface roughness, and disorders, transport properties in novel two-dimensional materials are primarily affected by lattice vibrations.…”

Section: Introductionmentioning

confidence: 99%

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Flexural and acoustic phonon-drag thermopower and electron energy loss rate in silicene

Ansari,

Ashraf,

Tripathi

et al. 2024

J. Phys.: Condens. Matter

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We have performed a comprehensive numerical and analytical examination of two crucial transport aspects in silicene: the phonon-drag thermopower,S^p,and the electron's energy loss rate,F_e. Specifically, our investigation is centered on their responses to out-of-plane flexural phonons and in-plane acoustic phonons in silicene, a two-dimensional allotrope of silicon as a function of electron temperature, T, and electron concentration, n, upto the room temperature. It is found that the calculated quantities have a non-monotonic dependence for the phonon modes for both parameters (T and n) considered while analytical results predict definite dependencies up to the complete low-temperature Bloch-Gruneisen (BG) regime. To provide a more comprehensive picture, we contrast the complete numerical outcomes with the approximated analytical BG results, revealing a convergence within a specific range of temperature and carrier concentration. In light of this convergence, we put forth suggestions to elucidate the underlying factors responsible for this behavior. A comparison based on the magnitude of the calculated quantities can be made from the figures between the two considered phonon modes, which clearly shows that the out-of-plane flexural phonons are effective throughout the considered temperature range. This observation leads us to posit that the dominating contribution of the out-of-plane flexural phonons modes hinges upon the deformation potential constant and phonon energy associated with the phonon mode. Our study carries significant implications for estimating the electrical and thermal properties of silicene and provides valuable insights for the development of devices based on silicene-based technologies.

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Section: Brief Formalism and Analytical Resultsmentioning

confidence: 99%

Section: Analytical Model For the Phonon Drag Thermopowermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flexural and acoustic phonon-drag thermopower and electron energy loss rate in silicene

Ansari,

Ashraf,

Tripathi

et al. 2024

J. Phys.: Condens. Matter

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Terahertz acoustic phonon Cerenkov emission in bilayer graphene

Ansari

Nafees

Ashraf

et al. 2022

Journal of Applied Physics

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We present a theoretical investigation on the generation of Cerenkov emission of terahertz acoustic phonons in bilayer graphene (BLG) in the presence of a driving dc electric field. We have numerically and analytically studied the Cerenkov phonon emission spectrum, [Formula: see text], and phonon intensity, [Formula: see text], dependence on the phonon frequency [Formula: see text], drift velocity [Formula: see text], electron temperature [Formula: see text], concentration n, and phonon emission angle [Formula: see text] in BLG with and without considering the chirality of the charge carriers. We find that the magnitude of [Formula: see text] increases at larger drift velocities and applied electric fields with the peak of the spectrum shifting toward the higher frequency side. The spectrum magnitude in BLG is found to be much enhanced as compared to conventional 2D semiconductors and transition metal dichalcogenides, which makes it viable for SASER and other practical device applications. The chiral nature of carriers strongly influences the [Formula: see text] behavior and sharpens the spectrum peak but with a decrease in the magnitude. The chirality favors the negative emission spectrum caused by the absorption of acoustic phonons. [Formula: see text] and [Formula: see text] are found to be strongly dependent on temperature but independent of carrier concentration in the equipartition regime. The study is significant from the point of application of BLG as an acousto/optoelectronic device and high-frequency phonon spectrometers.

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Energy relaxation rate and power loss density in graphene on GaAs substrate due to piezoelectric surface acoustic phonons

Arshia Khatoon,

Ansari,

Ashraf

2023

Int. J. Mod. Phys. B

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Electron-piezoelectric phonon interaction provides a significant extrinsic channel for energy relaxation in a graphene sheet placed on a polar substrate. We report in this paper our analytical and numerical investigations on energy relaxation rate and power loss density in graphene sheet on a polar substrate considering the electron-piezoelectric phonon scattering channel in the Boltzmann transport approach. We overcome the earlier crude approximations made to achieve the reported analytical results and compare the obtained results for their compliance with the numerical findings for the graphene sheet on the GaAs substrate. The obtained analytical expression for energy relaxation rate is valid for all temperatures and electron energies. The analytical result for power loss density limits its validity for low electron densities [Formula: see text]. It is observed that the relaxation rate due to surface piezoelectric phonons in graphene on GaAs substrate is directly proportional to temperatures above [Formula: see text], below which temperature independence is seen. Also, it is observed that the relaxation rate is linearly dependent on electron energy, [Formula: see text] at low temperatures, and [Formula: see text] independent at high temperatures. Moreover, the relaxation rate is electron density-independent for all (low to high) temperatures. The seemingly odd (from earlier reported behavior) temperature-independent, linearly dependent [Formula: see text] and n independent relaxation rate behavior for low temperatures is attributed to the approximation used so far in the phononic statistical occupation factor in deriving the relaxation rate in the low-temperature Bloch-Gruneisen (BG) regime. In undoped graphene, we have found that the power loss behavior follows a crossover from [Formula: see text] to [Formula: see text] behavior while moving from low [Formula: see text] to high [Formula: see text] electron temperature. This behavior contradicts the study by Zhang et al. [Phys. Rev. B 87, 075443 (2013)] and M. Ansari [Physica E: Low Dimens. Syst. Nanostruct. 131, 114722 (2021)] which reported low-temperature BG behavior of [Formula: see text]. This behavior is again attributed to using BG regime approximation for statistical occupation factors. Our findings are in agreement with the experimental work by Chen et al. [Nature Nanotechnol. 3, 206 (2008)] and You et al. [Appl. Phys. Lett. 115, 043104 (2019)].

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Phonon drag thermopower and energy loss rate in single and bilayer graphene due to piezoelectric surface acoustic phonons in Bloch-Gruneisen regime

Cited by 3 publications

References 51 publications

Flexural and acoustic phonon-drag thermopower and electron energy loss rate in silicene

Flexural and acoustic phonon-drag thermopower and electron energy loss rate in silicene

Terahertz acoustic phonon Cerenkov emission in bilayer graphene

Energy relaxation rate and power loss density in graphene on GaAs substrate due to piezoelectric surface acoustic phonons

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