Phonons transmission through atomic interface connecting two semi-infinite 2D lattices with different meshes

International Journal of Modern Physics B ◽

10.1142/s0217979222500126 ◽

2021 ◽

Author(s):

Smail Sait ◽

Boualem Bourahla

Keyword(s):

Lattice Dynamics ◽

Scattering Matrix ◽

Model Structure ◽

Coherent Phonon ◽

Elastic Coupling ◽

Phonon Modes ◽

Coherent Transport ◽

Coherent Coupling ◽

Discrete States ◽

Matching Technique

A calculation of the phonon contribution to the coherent transport between two-dimensional (2D) lattices is presented in this paper. The model structure is obtained by the juxtaposition of semi-infinites square ([Formula: see text] and triangular ([Formula: see text] leads, which thus define the nanojunction [Formula: see text]/[Formula: see text] and its inverse [Formula: see text]/[Formula: see text]. We determine, numerically and by simulation, the 2D interface observables for different values of masses and elastic coupling in the nanojunction zone. The local dynamics and atomic nanojunction response to the microscopic changes, in the interfacial domain, are subjects to our investigation. The theoretical formalism based on the matching technique is applied to describe the lattice dynamics and the evanescent phonon modes, in the two studied 2D interfaces. We mainly analyze the vibration spectra, the coherent phonon transmission/reflection and the phononic transmittance through the interface, as elements of a Landauer–Büttiker type scattering matrix. The obtained results show that the nanojunction domain is an effective phonon splitter and suggest that its characteristics may be controlled by varying its nanometric parameters. The observed fluctuations are due to the coherent coupling between continuum modes and the phonons’ discrete states induced by the connected atomic sites.

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Acoustic phonon lifetimes limit thermal transport in methylammonium lead iodide

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1812227115 ◽

2018 ◽

Vol 115 (47) ◽

pp. 11905-11910 ◽

Cited By ~ 27

Author(s):

Aryeh Gold-Parker ◽

Peter M. Gehring ◽

Jonathan M. Skelton ◽

Ian C. Smith ◽

Dan Parshall ◽

...

Keyword(s):

Lattice Dynamics ◽

Acoustic Phonon ◽

Optoelectronic Devices ◽

High Energy ◽

High Energy Resolution ◽

Phonon Coupling ◽

Lead Iodide ◽

Phonon Modes ◽

Electron Phonon Coupling ◽

Methylammonium Lead Iodide

Hybrid organic–inorganic perovskites (HOIPs) have become an important class of semiconductors for solar cells and other optoelectronic applications. Electron–phonon coupling plays a critical role in all optoelectronic devices, and although the lattice dynamics and phonon frequencies of HOIPs have been well studied, little attention has been given to phonon lifetimes. We report high-precision momentum-resolved measurements of acoustic phonon lifetimes in the hybrid perovskite methylammonium lead iodide (MAPI), using inelastic neutron spectroscopy to provide high-energy resolution and fully deuterated single crystals to reduce incoherent scattering from hydrogen. Our measurements reveal extremely short lifetimes on the order of picoseconds, corresponding to nanometer mean free paths and demonstrating that acoustic phonons are unable to dissipate heat efficiently. Lattice-dynamics calculations using ab initio third-order perturbation theory indicate that the short lifetimes stem from strong three-phonon interactions and a high density of low-energy optical phonon modes related to the degrees of freedom of the organic cation. Such short lifetimes have significant implications for electron–phonon coupling in MAPI and other HOIPs, with direct impacts on optoelectronic devices both in the cooling of hot carriers and in the transport and recombination of band edge carriers. These findings illustrate a fundamental difference between HOIPs and conventional photovoltaic semiconductors and demonstrate the importance of understanding lattice dynamics in the effort to develop metal halide perovskite optoelectronic devices.

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Lattice Dynamics of Gd1−xYxMn2O5 Investigated by Infrared Spectroscopy

Advances in Materials Science and Engineering ◽

10.1155/2017/3040254 ◽

2017 ◽

Vol 2017 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

Javed Ahmad ◽

Jawaria Mansoor ◽

Mehr Khalid Rehmani ◽

M. Tufiq Jamil ◽

Syed Hamad Bukhari

Keyword(s):

Infrared Spectroscopy ◽

Optical Conductivity ◽

Lattice Dynamics ◽

Lattice Vibration ◽

Systematic Investigation ◽

Structural Distortion ◽

Frequency Range ◽

Phonon Modes ◽

Frequency Shifts ◽

The Real

We present infrared (IR) reflectivity of Gd1-xYxMn2O5 with x = 0, 0.2, 0.4, 0.6, 0.8, and 1 in the frequency range 30–1000 cm−1. A total of 18 IR active phonons were observed for GdMn2O5 (x=0) and three additional phonons have been observed with increasing x, marking a total of 21 phonons in YMn2O5 (x=1). A systematic investigation was performed to map out the structural distortion through the lattice vibration and discuss the consequences of frequency shifts in phonon modes. In addition, we have calculated the real part of optical conductivity (σ1(ω)) which reflects the semiconducting nature of Gd1-xYxMn2O5.

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A First-Principles Study of Electron-Phonon Coupling of OsB2

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.597.113 ◽

2014 ◽

Vol 597 ◽

pp. 113-116

Author(s):

Yue Qin Wang ◽

Juan Gao ◽

Shao Ping Yan

Keyword(s):

Transition Temperature ◽

First Principles ◽

Linear Response ◽

Lattice Dynamics ◽

Superhard Material ◽

Superconducting Transition ◽

Phonon Coupling ◽

Phonon Modes ◽

Electron Phonon Coupling ◽

Coulomb Pseudopotential

We investigated the lattice dynamics and electron-phonon coupling (EPC) of superhard material OsB2by first-principles linear response calculations. The calculated EPC parameters for the optical phonon modes at Г indicate that the heavy Os atoms play the most important role in deciding the superconducting behavior, and there are sizeable contributions from lighter B atoms to EPC. Our calculated EPC constant is 0.42, and the estimated superconducting transition temperatureTcis 2.1 K using the Coulomb pseudopotentialμ*=0.125, in excellent agreement with the experimental ones.

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DYNAMICAL PROPERTIES OF AN ATOMIC INTERFACE BETWEEN bcc LATTICES

International Journal of Modern Physics B ◽

10.1142/s0217979214500726 ◽

2014 ◽

Vol 28 (10) ◽

pp. 1450072

Author(s):

GHANIA BELKACEMI ◽

BOUALEM BOURAHLA ◽

ANTOINE KHATER

Keyword(s):

Phonon Scattering ◽

Model System ◽

Localized States ◽

Interface Properties ◽

Transmission Spectra ◽

Coherent Phonon ◽

Matching Method ◽

Interface Zone ◽

Coherent Coupling ◽

Elastic Softening

A study of the phonon contribution to the interface properties between two bcc dissimilar solids is presented. The model system is obtained by the juxtaposition of two semi-infinite harmonic bcc lattices. The interface observables are numerically calculated for different cases of masses and elastic softening to hardening, to investigate how the local dynamics can respond to many environmental microscopic changes in the field interfacial domain. The theoretical formalism using simultaneously the Green's functions and the matching method is employed to describe the dynamics of the bcc system, the complete evanescent and the propagating fields. A calculation is presented for the vibration localized states, the coherent phonon transmission and the density of states (DOS), as element of a Landauer–Büttiker type scattering matrix. The system dynamics, the phonon scattering and the transmission spectra via the interface domain between bcc lattices and the DOS are analyzed as function of the atomic masses and the elastic force constants occurring in the nanojunction zone of the model system. Our results show that the interface zone is an effective phonon splitter and suggest that its characteristics may be controlled by varying its nanometric parameters. The observed fluctuations are due to the coherent coupling between continuum and discrete states induced by the interface domain.

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Generalization of the mode-matching technique to the problems of scattering by semi-infinite slow-wave structures

RADIOFIZIKA I ELEKTRONIKA ◽

10.15407/rej2020.04.010 ◽

2020 ◽

Vol 25 (4) ◽

pp. 10-17

Author(s):

S. Steshenko ◽

◽

Keyword(s):

Periodic Structure ◽

Slow Wave ◽

Wave Structure ◽

Scattering Matrix ◽

Slow Wave Structure ◽

Periodic Part ◽

Mode Matching ◽

Scattering Matrices ◽

Matching Technique ◽

Mode Matching Technique

Subject and purpose. The scattering matrix of a semi-infinite slow-wave structure formed by grooves in a rectangular waveguide is investigated. The purpose was to develop a method for calculating a semi-infinite periodic structure. Methods and methodology. A generalization of the mode-matching technique to semi-infinite periodic structures is built. The fields of the periodic part of the structure are expanded in series of the eigenmodes of the periodic structure, taking into account the condition at infinity, which makes it possible to obtain a linear matrix equation for finding the scattering matrix. Only the propagating modes of the periodic structure were considered. To make these expansions reliable the fields were matched at a period somewhat distant from the junction of the regular waveguide with the periodic one. Results. Matrix equations for determining the blocks of the scattering matrix of a semi-infinite structure are obtained. A number of investigations are carried out to check the reliability of the equations obtained. These include test of convergence, reciprocity, energy balance, and conservation of the scattering matrix while adding one period to a semi-infinite structure. The main confirmation was obtained by comparing the scattering matrix of a finite fragment of the slow-wave structure, obtained in two ways: through the scattering matrices of semi-infinite slow-wave structure and through a cascade assembly of the scattering matrices of the waveguide elements that make up the structure. Conclusions. An algorithm for calculating the scattering matrix of a semi-infinite structure is obtained. It can be used to build a rigorous hot model of vacuum electronics devices using slow-wave structures.

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Lattice dynamics in CePd2Al2 and LaPd2Al2

Scientific Reports ◽

10.1038/s41598-021-99904-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Petr Doležal ◽

Petr Cejpek ◽

Satoshi Tsutsui ◽

Koji Kaneko ◽

Dominik Legut ◽

...

Keyword(s):

Lattice Dynamics ◽

Phonon Dispersion ◽

Elastic Interaction ◽

Bound State ◽

Dispersion Curves ◽

Phonon Modes ◽

Phonon Dispersion Curves ◽

X Ray Scattering ◽

Oppenheimer Approximation ◽

Good Agreement

AbstractThe interaction between phonons and 4f electrons, which is forming a new quantum state (quasi-bound state) beyond Born-Oppenheimer approximation, is very prominent and lattice dynamics plays here a key role. There is only a small number of compounds in which the experimental observation suggest such a scenario. One of these compounds is CePd2Al2. Here the study of phonon dispersion curves of (Ce,La)Pd2Al2 at 1.5, 7.5, 80 and 300 K is presented. The inelastic X-ray scattering technique was used for mapping the phonon modes at X and Z points as well as in Λ and Δ directions, where the symmetry analysis of phonon modes was performed. The measured spectra are compared with the theoretical calculation, showing very good agreement. The measurements were performed in several Brillouin zones allowing the reconstruction of phonon dispersion curves. The results are discussed with respect to the magneto-elastic interaction and are compared with other cerium compounds. The phonon mode symmetry A1g was found to be unaffected by the interaction, which is in contrast to previous assumptions.

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