Brillouin zone unfolding method for effective phonon spectra

Boykin, Timothy B.; Ajoy, Arvind; Ilatikhameneh, Hesameddin; Povolotskyi, Michael; Klimeck, Gerhard

doi:10.1103/physrevb.90.205214

Cited by 22 publications

(18 citation statements)

References 34 publications

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“…Note that if the phonon-associated property is zero, such as the electron-phonon coupling strength in zigzag graphene nanoribbons with even dimers (due to the selection rule of the parity conservation) [31], then the contribution of each BM is also zero. Similar projection procedures have been applied for other purposes, such as unfolding the phonon dispersions of a supercell into the 1st BZ of the primitive cell [32][33][34][35][36][37].…”

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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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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“…c 11 and c 12 ) of the material. The Keating model is known to be a suitable model for calculation of the atomistic strain in self-assembled QDs [11,[21][22][23] and phonon dispersion in nanowires and in bulk [24]. Cuboid and dome shaped QDs with different dimensions have been simulated using the Keating model to study the behavior of strain with different QD dimensions, shapes, and materials.…”

Section: Atomistic Simulationmentioning

confidence: 99%

Universal Behavior of Atomistic Strain in Self-Assembled Quantum Dots

Ilatikhameneh

Ameen

Klimeck

et al. 2016

IEEE J. Quantum Electron.

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Self-assembled quantum dots (QDs) are highly strained heterostructures. the lattice strain significantly modifies the electronic and optical properties of these devices. A universal behavior is observed in atomistic strain simulations (in terms of both strain magnitude and profile) of QDs with different shapes and materials. In this paper, this universal behavior is investigated by atomistic as well as analytic continuum models. Atomistic strain simulations are very accurate but computationally expensive. On the other hand, analytic continuum solutions are based onassumptions that significantly reduce the accuracy of the strain calculations, but are very fast. Both techniques indicate that the strain depends on the aspect ratio (AR) of the QDs, and not on the individual dimensions. Thus simple closed form equations are introduced which directly provide the atomistic strain values inside the QD as a function of the AR and the material parameters. Moreover, the conduction and valence band edges E C/V and their effective masses m * C/V of the QDs are dictated by the strain and AR consequently. The universal dependence of atomistic strain on the AR is useful in many ways; Not only does it reduce the computational cost of atomistic simulations significantly, but it also provides information about the optical transitions of QDs given the knowledge of E C/V and m * C/V from AR. Finally, these expressions are used to calculate optical transition wavelengths in InAs/GaAs QDs and the results agree well with experimental measurements and atomistic simulations.

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“…Here we also analyze the contributions of different chemical elements in the unfolded band structures. In previous approaches [4,6,13], it was not clear how to investigate the contributions of different chemical elements to the unfolded band structures. This issue largely limits our understanding about the band structures of disordered systems.…”

Section: Introductionmentioning

confidence: 99%

Mode decomposition based on crystallographic symmetry in the band-unfolding method

et al. 2017

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The band-unfolding method is widely used to calculate the effective band structures of a disordered system from its supercell model. The unfolded band structures show the crystallographic symmetry of the underlying structure, where the difference of chemical components and the local atomic relaxation are ignored. It has been, however, still difficult to decompose the unfolded band structures into the modes based on the crystallographic symmetry of the underlying structure, and therefore detailed analyses of the unfolded band structures have been restricted. In this study, we develop a procedure to decompose the unfolded band structures according to the small representations (SRs) of the little groups. For this purpose, we derive the projection operators for SRs based on the group representation theory. We also introduce another type of projection operators for chemical elements, which enables us to decompose the unfolded band structures into the contributions of different combinations of chemical elements. Using the current method, we investigate the phonon band structure of disordered face-centered cubic Cu 0.75 Au 0.25 , which has large variations of atomic masses and force constants among the atomic sites due to the chemical disorder. We find several peculiar behaviors such as discontinuous and split branches in the unfolded phonon band structure. They are found to occur because different combinations of the chemical elements contribute to different regions of frequency.

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Brillouin zone unfolding method for effective phonon spectra

Cited by 22 publications

References 34 publications

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

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

Universal Behavior of Atomistic Strain in Self-Assembled Quantum Dots

Mode decomposition based on crystallographic symmetry in the band-unfolding method

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