Mermin-Wagner theorem, flexural modes, and degraded carrier mobility in two-dimensional crystals with broken horizontal mirror symmetry

Fischetti, Massimo V.; Vandenberghe, William G.

doi:10.1103/physrevb.93.155413

Cited by 91 publications

(77 citation statements)

References 69 publications

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“…Recently, the intrinsic mobility of 2D materials with broken planar mirror reflection (σ h ) symmetry, such as, e.g., silicene and germanene, has been demonstrated to be very low [15,16]. The explanation is found in a strong coupling to the flexural-acoustic (ZA) membrane mode in combination with an exceedingly high occupation of this mode due to its quadratic dispersion and constant density of phonon states (DOS) [17].…”

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confidence: 99%

Flexural-Phonon Scattering Induced by Electrostatic Gating in Graphene

2017

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Graphene has an extremely high carrier mobility partly due to its planar mirror symmetry inhibiting scattering by the highly occupied acoustic flexural phonons. Electrostatic gating of a graphene device can break the planar mirror symmetry yielding a coupling mechanism to the flexural phonons. We examine the effect of the gate-induced one-phonon scattering on the mobility for several gate geometries and dielectric environments using first-principles calculations based on density functional theory (DFT) and the Boltzmann equation. We demonstrate that this scattering mechanism can be a mobility-limiting factor, and show how the carrier density and temperature scaling of the mobility depends on the electrostatic environment. Our findings may explain the high deformation potential for in-plane acoustic phonons extracted from experiments and furthermore suggest a direct relation between device symmetry and resulting mobility.

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confidence: 99%

Flexural-Phonon Scattering Induced by Electrostatic Gating in Graphene

2017

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“…Particularly, as has been shown in Ref. 24, single-phonon processes associated with flexural modes are highly relevant for non-mirror-symmetric 2D Dirac materials like silicene and germanene. Such processes correspond to additional terms in Eq.…”

Section: B Electron-phonon Scatteringmentioning

confidence: 75%

Interplay between in-plane and flexural phonons in electronic transport of two-dimensional semiconductors

Руденко

Lugovskoi²,

Mauri³

et al. 2019

Phys. Rev. B

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Out-of-plane vibrations are considered as the dominant factor limiting the intrinsic carrier mobility of suspended two-dimensional materials at low carrier concentrations. Anharmonic coupling between in-plane and flexural phonon modes is usually excluded from the consideration. Here we present a theory for the electron-phonon scattering, in which the anharmonic coupling between acoustic phonons is systematically taken into account. Our theory is applied to the typical group V twodimensional semiconductors: hexagonal phosphorus, arsenic, and antimony. We find that the role of the flexural modes is essentially suppressed by their coupling with in-plane modes. At dopings lower than 10 12 cm −2 the mobility reduction does not exceed 30%, being almost independent of the concentration. Our findings suggest that compared to in-plane phonons, flexural phonons are considerably less important in the electronic transport of two-dimensional semiconductors, even at low carrier concentrations.

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“…It is possible that in other systems the property is mainly governed by the phonons far from the Γ point, then a larger difference between the results obtained using the projection method and the energy method can be anticipated, which deserves further separate studies. The dominance of ZA-phonon induced scattering can be explained by the parabolic dispersion of the ZA mode in ultrathin material and the absence of the mirror symmetry in the atomic structure of 2D Sb, which give rise to a large density of ZA phonons that can scatter the electrons [45]. If the ZA and/or LA phonons can be frozen, which may be achieved using adhesive substrate and/or strain, then the electron mobility in 2D Sb can be improved.…”

Section: Resultsmentioning

confidence: 99%

How to resolve a phonon-associated property into contributions of basic phonon modes

Cheng¹,

Zhang²,

Liu³

2019

J. Phys. Mater.

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Many properties of materials are associated with phonons. To better understand the phonon-property relation, it is a common practice to decompose the phonon-associated property into the contributions of basic phonon/vibration modes (e.g. longitudinal/transverse acoustic/optical mode), and identify the mode(s) that dominate(s) the property. The existing methods rely on labelling the phonon into one of the basic modes (BMs), however, the vibration characteristics of many phonons are different from the definitions of BMs, indicating these methods may give wrong decomposition results. Here we present a new method based on treating the phonon as a mixture of the BMs. By aligning the wave vectors and then projecting the phonon eigenvector onto the eigenvectors of the BMs, we can obtain the weights of the BMs on the given phonon, which can be used to quantify the contribution of each BM to the property. As an example, we apply this method to unravel the phonon modes that dominate the scattering of the electrons at the conduction band edge in two-dimensional antimony, an emerging semiconductor that has attracted great interest for electronics, but its mobility-limiting factors remain unclear. We find that the electron scattering is dominated by the out-of-plane acoustic phonon mode followed by the longitudinal acoustic mode, which are different from the results of other methods. Our method is generally applicable to different kinds of phonon-related properties and to all crystal materials.

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Mermin-Wagner theorem, flexural modes, and degraded carrier mobility in two-dimensional crystals with broken horizontal mirror symmetry

Cited by 91 publications

References 69 publications

Flexural-Phonon Scattering Induced by Electrostatic Gating in Graphene

Flexural-Phonon Scattering Induced by Electrostatic Gating in Graphene

Interplay between in-plane and flexural phonons in electronic transport of two-dimensional semiconductors

How to resolve a phonon-associated property into contributions of basic phonon modes

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