Готові списки джерел за темами / Interaction des phonons

Добірка наукової літератури з теми "Interaction des phonons"

Автор: Grafiati

Опубліковано: 8 червня 2024

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Статті в журналах з теми "Interaction des phonons":

Khvesyuk, V. I., W. Qiao, and A. A. Barinov. "Kinetics of Phonon Interaction Taken into Account in Determining Thermal Conductivity of Silicon." Herald of the Bauman Moscow State Technical University. Series Natural Sciences, no. 3 (102) (June 2022): 57–68. http://dx.doi.org/10.18698/1812-3368-2022-3-57-68.

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The thorough study of the heat carriers --- quasiparticles --- phonons interaction resulted in a pioneering method for calculating the thermal conductivity of nonmetallic solids. As the interactions of phonons are much more complicated than those of usual atoms and molecules, it is necessary to take into account the presence of two types of phonons with different properties; the decay of one phonon into two or the fusion of two phonons into one as a result of interaction; the presence of two types of interaction of phonons, one of which is elastic, the other is inelastic (moreover, the type of interaction results from solving the energy and quasi-momentum conservation equations). The existing methods for determining thermal conductivity, which typically involve solving the Boltzmann transport equation, use the iteration method, whose parameter is the average time between successive phonon interactions, and the calculation results provide little information on all types of interactions. In this research, we developed a method of direct Monte Carlo simulation of phonon diffusion with strict account for their interaction owing to the energy and quasi-momentum conservation laws. Calculations of the thermal conductivity coefficient for pure silicon in the temperature range of 100---300 K showed good agreement with the experiment and calculations of other authors, and also made it possible to consider the phonon kinetics in detail

Xu, Jing, Qingshan Yuan, and Hong Chen. "Phase Transition in a Two-State Chain Interacting with a Phonon Bath." International Journal of Modern Physics B 12, no. 14 (June 10, 1998): 1485–93. http://dx.doi.org/10.1142/s0217979298002891.

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The properties of a two-state chain interacting with a phonon bath is studied in this paper. We discuss the renormalization of the single pseudospin tunneling parameter by phonons' interaction, as well as other pseudospins' correlation. We find that for Ohmic dissipation, the correlation between pseudospins vanishes and the phonons' interaction induces the localization–delocalization transition. For our discussed super-Ohmic dissipation, the phonons' interaction only reduces the tunneling parameter and does not induce phase transition. In this case the pseudospins' correlation has its effect and reduces the tunneling parameter at weak coupling. In addition, some application of our results is also discussed.

Capone, M., C. Castellani, and M. Grilli. "Electron-Phonon Interaction in Strongly Correlated Systems." Advances in Condensed Matter Physics 2010 (2010): 1–18. http://dx.doi.org/10.1155/2010/920860.

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The Hubbard-Holstein model is a simple model including both electron-phonon interaction and electron-electron correlations. We review a body of theoretical work investigating, the effects of strong correlations on the electron-phonon interaction. We focus on the regime, relevant to high-Tcsuperconductors, in which the electron correlations are dominant. We find that electron-phonon interaction can still have important signatures, even if many anomalies appear, and the overall effect is far from conventional. In particular in the paramagnetic phase the effects of phonons are much reduced in the low-energy properties, while the high-energy physics can still be affected by phonons. Moreover, the electron-phonon interaction can give rise to important effects, like phase separation and charge-ordering, and it assumes a predominance of forward scattering even if the bare interaction is assumed to be local (momentum independent). Antiferromagnetic correlations reduce the screening effects due to electron-electron interactions and revive the electron-phonon effects.

DOLOCAN, ANDREI, VOICU OCTAVIAN DOLOCAN, and VOICU DOLOCAN. "SOME ASPECTS OF THE ELECTRON-BOSON INTERACTION AND OF THE ELECTRON-ELECTRON INTERACTION VIA BOSONS." Modern Physics Letters B 21, no. 01 (January 10, 2007): 25–36. http://dx.doi.org/10.1142/s0217984907012335.

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By using a Hamiltonian of interaction between fermions via bosons1 we derive some properties of the electro-phonon and electron-photon interaction and also of the electron-electron interaction. We have obtained that in a degenerate electron gas there is an attraction between two electrons via acoustical phonons. Also, in certain conditions, there may be an attraction between two electrons via longitudinal optical phonons. Although our expressions for the polaron energy in both cases of the acoustical and longitudinal optical phonons are different from that obtained in the standard theory, their magnitudes are the same with these and they are in good agreement with experimental data. The total emission rate of an electron against a phonon system at absolute zero is directly proportional to the electron momentum. Also, an attraction between two electrons may appear via photons.

Zhang, Li, Hong-Jing Xie, and Chuan-Yu Chen. "Electron-Phonon Interaction in a Multi-Shell Spherical Nanoheterosystem." Modern Physics Letters B 17, no. 20n21 (September 10, 2003): 1081–94. http://dx.doi.org/10.1142/s0217984903006165.

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Under the dielectric continuum approximation, the confined longitudinal-optical (LO) phonon and interface-optical (IO) phonon modes of a multi-shell spherical nanoheterosystem are discussed. To describe the vibrations of the LO phonons, a proper eigenfunction for LO phonon modes in the core region is adopted and a legitimate eigenfunction for LO modes in the shell region is constructed. To deal with the IO phonon modes, determinant methods are employed, and the determinant deciding the frequencies of IO phonon modes are obtained. The quantized LO and IO phonons fields as well as their corresponding electron-phonon interaction Hamiltonians are also derived.

Manuel, Cristina, and Laura Tolos. "Transport Properties of Superfluid Phonons in Neutron Stars." Universe 7, no. 3 (March 5, 2021): 59. http://dx.doi.org/10.3390/universe7030059.

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We review the effective field theory associated with the superfluid phonons that we use for the study of transport properties in the core of superfluid neutrons stars in their low temperature regime. We then discuss the shear and bulk viscosities together with the thermal conductivity coming from the collisions of superfluid phonons in neutron stars. With regard to shear, bulk, and thermal transport coefficients, the phonon collisional processes are obtained in terms of the equation of state and the superfluid gap. We compare the shear coefficient due to the interaction among superfluid phonons with other dominant processes in neutron stars, such as electron collisions. We also analyze the possible consequences for the r-mode instability in neutron stars. As for the bulk viscosities, we determine that phonon collisions contribute decisively to the bulk viscosities inside neutron stars. For the thermal conductivity resulting from phonon collisions, we find that it is temperature independent well below the transition temperature. We also obtain that the thermal conductivity due to superfluid phonons dominates over the one resulting from electron-muon interactions once phonons are in the hydrodynamic regime. As the phonons couple to the Z electroweak gauge boson, we estimate the associated neutrino emissivity. We also briefly comment on how the superfluid phonon interactions are modified in the presence of a gravitational field or in a moving background.

Sachkov, V. A. "The influence of atoms of second coordination sphere on phonon dispersion of diamond." Omsk Scientific Bulletin, no. 173 (2020): 111–13. http://dx.doi.org/10.25206/1813-8225-2020-173-111-113.

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Within the framework of the phenomenological model of twoparticle interaction, the effect of the interaction energy of atoms from the second coordination sphere on the phonon dispersion is considered. This approach makes it possible to vary the growth of the phonon frequency relative to the optical phonon in the center of the Brillun zone. The effects of the contribution to the Raman spectra from longitudinal optical phonons with frequencies higher than their frequency at the center of the Brillouin zone are discussed. The contribution to the frequency of interaction of atoms from the second coordination sphere for some phonons is obtained in an explicit form. The formulas obtained will be useful for calculating the spectra of Raman scattering of light by optical phonons localized in diamond nanocrystals

Maslov A. Yu. and Proshina O. V. "Polaron mass of carriers in a thin film on ionic substrates." Semiconductors 56, no. 9 (2022): 675. http://dx.doi.org/10.21883/sc.2022.09.54134.9901.

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A new approach to establishing a strong electron--phonon interaction in heterostructures is proposed. A three-layer structure consisting of an ionic substrate, a semiconductor film, and a covering dielectric (with air or vacuum possibly serving as such a dielectric) is examined. Interface optical phonons emerge near the heterointerface. Their parameters are governed by the dielectric properties of the substrate. It is demonstrated that the effective mass of carriers in the film is altered in the presence of interface phonons. Depending on the substrate ionicity, the magnitude of this change may vary from several tens to hundreds of percent. It is shown that the conditions for strong electron--phonon interaction may be established in a large number of semiconductor films. Measurements of the effective mass of carriers in identical films positioned on different substrates should make it possible to identify a transition from a weak electron--phonon interaction to a strong one. Keywords: electron--phonon interaction, effective mass, interface phonons, polaron, thin films.

PAUL, PRABASAJ, and DANIEL C. MATTIS. "EXTINCTION OF SPIN INTERACTIONS IN THE 2D KONDO LATTICE." International Journal of Modern Physics B 09, no. 24 (October 30, 1995): 3199–208. http://dx.doi.org/10.1142/s0217979295001221.

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A two-dimensional Kondo lattice with inter-site interaction is studied using a canonical transformation to eliminate interactions. Our approach is patterned on Bardeen and Pines' elimination of electron–phonon interaction. It is shown that interactions are eliminated at nonzero temperatures in the thermodynamic limit, in a manner differing radically from the case of phonons.

SINGH, NAVINDER. "HOT ELECTRON RELAXATION IN A METAL NANOPARTICLE: ELECTRON SURFACE-PHONON INTERACTION." Modern Physics Letters B 18, no. 24 (October 20, 2004): 1261–65. http://dx.doi.org/10.1142/s0217984904007797.

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The relaxation of hot electrons is considered in a metal nanoparticle. When the particle size is of the order of electron mean free path, the main channel of hot electron energy loss is through surface-phonon generation, rather than bulk phonon generation. A calculation for the hot electron relaxation by the generation of surface-phonons is given, assuming that electrons and surface-phonons are described by their equilibrium Fermi and Bose distribution functions. The assumption is valid because the time required to establish equilibrium in the electron gas is much less than the time for achieving equilibrium between the electrons and the surface-phonons. The expressions obtained for low-temperature and high-temperature regimes are inversely proportional to the radius of the particle. This shows that size dependency of electron surface-phonon energy exchange arises from the geometric effect.

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Дисертації з теми "Interaction des phonons":

Iskandar, Abdo. "Phonon Heat Transport and Photon-phonon Interaction in Nanostructures." Thesis, Troyes, 2018. http://www.theses.fr/2018TROY0010.

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Cette thèse avait pour cadre, le contrôle du transport thermique via les phonons et leur interaction avec des photons dans des nanostructures. Le manuscrit comprend cinq chapitres. Dans le premier, nous introduisons la physique des phonons et excitations élémentaires optiques de la matière. Le deuxième chapitre fournit une description des procédés de croissance, techniques de structuration et techniques de caractérisation utilisées. Dans le troisième chapitre, nous démontrons qu’à la fois, phonons et photons peuvent être confinés et interagir dans une même nanostructure. Dans le quatrième chapitre, nous montrons expérimentalement que le spectre de phonons d'un matériau peut être modifié par des mécanismes d'hybridation entre des modes de surface introduits par une nanostructuration et les modes normaux du matériau massif. Nous montrons que la forme et la taille des nanostructures sur la surface du matériau ont des effets sur le spectre de phonons du substrat. Dans le cinquième chapitre, nous montrons qu'à basse température (inférieure à 4 K), la chaleur spécifique des nanofils est équivalente à celle d'un cristal essentiellement bidimensionnel. Encore plus étonnant à l'interface entre les nanofils et le substrat, nous avons mis en évidence une transition entre une transmission élastique spéculaire et une transmission élastique diffuse. Lorsque la température augmente on observe alors une transition entre une diffusion élastique et une diffusion inélastique. L’ensemble de ces résultats laisse entrevoir des perspectives intéressantes pour le contrôle des propriétés thermiques de matériaux massifs par nanostructuration de surface
In this dissertation, we investigate phonon heat transport and phonon interaction with optical elementary excitations in nanostructures. In the first chapter, we present an introduction to the physics of phonons and optical elementary excitations in nanostructured materials. The second chapter provides a detailed description of the samples growth and fabrication procedures and the various characterization techniques used. In the third chapter, we demonstrate that phonons and photons of different momenta can be confined and interact with each other within the same nanostructure. In the fourth chapter, we present experimental evidence on the change of the phonon spectrum and vibrational properties of a bulk material through phonon hybridization mechanisms. We demonstrate that the phonon spectrum of a bulk material can be altered by hybridization between confined phonon modes in nanostructures introduced on the surface of the material and the underlying bulk phonon modes. Shape and size of the nanostructures made on the surface of the substrate have strong effects on the phonon spectrum of the bulk material itself. In the fifth chapter, we demonstrate that at low temperatures (below 4 K) the nanowire specific heat exhibits a clear contribution from an essentially two-dimensional crystal. We also demonstrate that transitions from specular to diffusive elastic transmission and then from diffusive elastic to diffusive inelastic transmission occur at the interface between nanowires and a bulk substrate as temperature increases. Perspectives include the control of bulk material thermal properties via surface nanostructuring

Poyser, Caroline Louise. "The interaction of coherent acoustic phonons with electrons in semiconductor superlattices." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/30591/.

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This thesis presents a study of the electron-phonon interaction in an n-doped weakly coupled semiconductor superlattice (SL). Two experiments were performed which studied different aspects of this interaction. Firstly, a coherent phonon optics chip was designed. This was used in an experiment where a phonon beam was passed through the SL while an electrical bias was applied to it. The experiment provided a sensitive measurement of the effects caused by bias in the SL on the phonon beam. Secondly, a train of strain pulses was passed through the SL and the charge transferred in the device due to the strain was investigated. A coherent phonon optics chip was formed using a semiconductor superlattice as a transducer structure and a p-i-n photodiode as a coherent phonon detector on the opposite side of the substrate. The doped weakly coupled superlattice structure, which is the main subject of investigation in this thesis was grown between the transducer and detector structures. Optical access mesas were processed on both sides of the substrate to allow the application of bias to both the doped superlattice and the p-i-n structures. A photocurrent pump-probe experiment was then performed using a femtosecond laser to excite the transducer structure and activate the detection mechanism. The application of bias to the weakly coupled SL was found to cause a small attenuation to the 378 GHz phonon beam passing through it. An investigation of the possible causes of this attenuation ruled out several trivial explanations, suggesting that it was caused by the interaction between electrons and phonons in the structure. The active control of phonon amplitude by electrical means has not previously been demonstrated and may offer exciting new prospectives for phonon devices and experiments. The coherent phonon optics technique was shown to be very sensitive and it will be a useful technique to increase our understanding of future acousto-electric devices. The electrical signal that acoustic excitation caused in the SL device was investigated using a pulse shaping technique in combination with an amplified femtosecond laser. A Fabry-Perot cavity was used in the laser path to create a train of equally spaced laser pulses with an adjustable pulse spacing. Focusing these pulses on an aluminium film transducer creates a train of equally spaced acoustic pulses simulating a monochromatic acoustic wave packet. The SL was processed and electrically contacted so that the charge transferred through it due to the acoustic pulse train could be monitored using a 12.5 GHz-bandwidth digital oscilloscope. The variation in charge transfer seen as a function of the DC bias applied to the device and as a function of the total energy of the acoustic pulse train was investigated. The behavior was compared to a theoretical model developed in the style of previous theories of electrical conversion in SLs excited by electromagnetic waves. The dependencies of the charge transfer on the bias and energy of the pulse train were well reproduced in the theory. The theory predicted that magnitude of the signal in the superlattice was independent of the frequency of the acoustic pulse train. This was verified by measuring the frequency dependence of the signal seen for a variety of transducer films. The frequency dependencies seen were well explained through simulations presuming the device response was independent of train frequency. This confirms the predictions of the theory. Both the experiments detailed in this thesis have helped increase our understanding of the nature of electron-phonon interactions in superlattices. It is hoped that a fuller understanding of these interactions may be instrumental in the creation of exciting new acousto-electrical devices.

El-Jallal, Said. "Cristaux phoxoniques et propriétés optomécaniques : interaction des photons et des phonons." Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10047/document.

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Dans cette thèse, on étudie l’interaction optomécanique dans les cavités des cristaux phoxoniques définis comme des cristaux à la fois photonique et phononique. Ces structures périodiques peuvent présenter simultanément des bandes interdites absolues pour les ondes électromagnétiques et pour les ondes acoustiques. L’introduction de défauts tels qu’une cavité dans le cristal permet d’obtenir à la fois des photons et des phonons localisés. Ce confinement simultané des deux excitations à l’intérieur d’une même cavité permet d’exalter leur interaction et d’envisager de nouveaux dispositifs acousto-optiques à l’échelle submicronique. Nous avons étudié théoriquement cette interaction optomécanique dans différentes structures de cristaux phoxoniques (2D, plaques et nanoguide structuré). Nous avons mis en évidence l’effet du changement du matériau et de la longueur d’onde incidente sur le couplage optomécanique. Les résultats pour le nanoguide structuré ont été comparés à des résultats expérimentaux réalisés par nos partenaires. Enfin, le couplage phonon-plasmon est abordé à la fois en terme de premiers résultats et de perspective
In this thesis, we study optomechanic interactions in phoxonic crystals which are defined as dual phononic/photonic crystals that can exhibit simultaneously phononic and photonic band gaps. The existence of absolute band gaps allows the simultaneous confinement of both waves that, in turn, can produce the enhancement of their interaction for the purpose of novel and high-performance optomechanical and acousto-optic devices and applications. A main objective is the modulation of light by acoustic waves when both excitations are confined inside the same cavity or propagate with a slow group velocity inside a waveguide. We have studied theoretically the optomechanic interactions in different (2D, slabs and strip) phoxonic crystals cavities. We have demonstrated the dependence of these optomechanic interactions as a function of both the nature of the material and the incoming optical wavelength. The results for strip waveguides have been compared with experimental results performed by our partners. Finally, as a perspective, we began to study the phonon-plasmon coupling

Reigue, Antoine. "Boîte quantique en interaction avec son environnement : excitation résonante pour l'étude des processus de décohérence." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066731/document.

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Les boîtes quantiques (BQ) semi-conductrices possèdent une structure électronique discrète qui en fait une excellente source de photons uniques et indiscernables. Elles sont ainsi devenues un système très attractif pour des futures applications en information quantique, grâce à la possibilité de les intégrer dans des nano-dispositifs permettant un couplage efficace lumière-matière. Cependant, les BQs constituent par nature un système ouvert en interagissant fortement avec l'environnement solide, une des conséquences étant la destruction partielle de la cohérence des photons émis. Dans ce travail, nous avons choisi d'utiliser une BQ comme sonde très sensible de ces interactions. Des expériences d'interférences à deux photons, de type Hong-Ou-Mandel, sous excitation résonante et en fonction de la température, nous ont permis d’étudier l'interaction entre une BQ et les phonons acoustiques de la matrice cristalline environnante. En combinant nos résultats expérimentaux et un modèle théorique microscopique, nous avons identifié deux processus distincts responsables de la perte d’indiscernabilité : le premier dû aux transitions réelles par absorption-émission de phonons, le deuxième à cause de transitions virtuelles, processus du deuxième ordre, dues à la présence d’états excités de plus haute énergie dans la boîte. Nous avons par ailleurs étudié des échantillons dopés permettant d’appliquer un champ électrique sur le plan de BQ, mettant en évidence que le contrôle de l’état de charge d’une BQ permet sont excitation résonante systématique
Developments in quantum information processes require the use of solid state qubits that would emit on demand single and indistinguishable photons. Semiconductor quantum dots (QDs) show an atom-like spectrum which makes them attractive in this regard. However, a single QD constitutes an open quantum system coupled to its surrounding solid-state environment, the phonon bath and the fluctuating electrostatic environment. This has important consequences on the coherence properties of the electronic system and the QD is a probe to study these fundamental interactions. Using Fourier spectroscopy and temperature-dependent resonant HOM experiments we show that these two mechanisms occur on very different time scales: spectral diffusion is a slow dephasing process acting on microseconds, while phonon interaction takes place in less than one ns. Then, the loss of ndistinguishability in HOM measurements is only related to dephasing induced by the coupling to the phonon bath. The TPI visibility is preserved around 85 % at low temperature, followed by a rapid loss of coherence. To fully understand the experimental results we developed a mircroscopic model for the electron-phonon interaction which allow to obtain analytic expressions for the dephasing rates. Below 10K the relaxation of the vibrational lattice is the dominant contribution to the loss of TPI visibility. This process corresponds to real phonon transitions resulting in a broad phonon sideband in the QD emission spectra. Above 10K, virtual phonon transitions to higher lying excited states become the dominant dephasing mechanism, leading to broadening of the zero phonon line and a corresponding rapid decay in the visibility

Isaia, Jean-Noël. "Niveaux électroniques et interaction électron - phonons dans les boîtes quantiques d'InAs/GaAs." Paris 6, 2003. http://www.theses.fr/2003PA066443.

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Geondzhian, Andrey. "Resonant inelastic X-ray scattering as a probe of exciton-phonon coupling." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAY077/document.

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Les phonons contribuent à la diffusion inélastique résonante des rayons X (RIXS) du fait du couplage entre les degrés de liberté électronique et ceux du réseau. Contrairement à d'autres techniques sensibles aux interactions électron-phonon, la technique RIXS peut donner accès aux constantes de couplage dépendantes du moment. Des informations sur la dispersion de l'interaction électron-phonon sont très précieuses dans le contexte de la supraconductivité anisotrope conventionnelle et non conventionnelle.Nous avons considéré la contribution des phonons sur la diffusion RIXS d’un point de vue théorique. Contrairement aux études précédentes nous soulignons le rôle du couplage du réseau avec les trous de cœur. Notre modèle, avec les paramètres obtenus ab-initio, montre que même dans le cas d'un trou de coeur profond, la technique RIXS sonde le couplage exciton-phonon plutôt qu’un couplage direct électron-phonon.Cette différence conduit à des écarts quantitatifs et qualitatifs pour le couplage électron-phonon implicite par rapport à l'interprétation standard dans la littérature. Ainsi, notre objectif est de développer une approche rigoureuse pour quantifier le couplage électron-phonon dans le contexte des mesures de diffusion RIXS. La possibilité de reproduire avec précision les résultats expérimentaux à partir des calculs ab-initio, sans recourir à des paramètres ajustés, doit être considérée comme le test ultime d'une compréhension correcte de la contribution des phonons sur la diffusion RIXS.Nous commençons notre travail en considérant uniquement l’interaction trou de coeur-phonon dans le contexte de la spectroscopie par photoémission de rayons X. Nous combinons un calcul ab-initio de la fonction de réponse en espace réel avec des techniques de fonctions de Green à plusieurs corps pour reproduire les bandes latérales vibrationnelles dans les molécules SiX4 (X = H, F). L'approche que nous avons développée peut être appliquée aux matériaux cristallins.Nous examinons ensuite la contribution des phonons aux spectres d'absorption des rayons X. Contrairement aux excitations chargées générées par la photoémission par rayons X, l'absorption des rayons X crée une excitation neutre que nous approchons en tant que trou de cœur et électron excité. Nous résolvons d’abord la partie électronique du problème au niveau de l’équation de Bethe-Salpeter, puis nous habillons la quasi-particule excitonique à 2 particules résultante avec les interactions exciton-phonon en utilisant l’Ansatz des cumulants. La viabilité de cette méthode a été testée en calculant le seuil K XAS de la molécule N2 et le seuil K d’Oxygène de l’acétone. Les spectres vibrationnels obtenus concordent avec les résultats expérimentaux.Enfin, nous construisons une formulation hybride de la section transversale RIXS qui préserve la sommation explicite sur un petit nombre d'états finals, mais remplace la sommation sur les états intermédiaires, ce qui pourrait être extrêmement coûteux, par une fonction de Green. Nous avons obtenu un développement de la fonction de Green et dérivé des solutions analytiques exactes (dans la limite de non-recul) et approximatives. Le formalisme a de nouveau été testé sur le seuil K de l'acétone et est bien en accord avec l'expérience. En perspectives des travaux futurs, nous discutons de l’applicabilité de notre formalisme aux matériaux cristallins
Phonons contribute to resonant inelastic X-ray scattering (RIXS) as a consequence of the coupling between electronic and lattice degrees of freedom. Unlike other techniques that are sensitive to electron-phonon interactions, RIXS can give access to momentum dependent coupling constants. Information about the dispersion of the electron-phonon interaction is highly desirable in the context of understanding anisotropic conventional and unconventional superconductivity.We considered the phonon contribution to RIXS from the theoretical point of view. In contrast to previous studies, we emphasize the role of the core-hole lattice coupling. Our model, with parameters obtained from first principles, shows that even in the case of a deep core-hole, RIXS probes exciton-phonon coupling rather than a direct electron-phonon coupling.This difference leads to quantitative and qualitative deviations from the interpretation of the implied electron-phonon coupling from the standard view expressed in the literature. Thus, our objective is to develop a rigorous approach to quantify electron-phonon coupling within the context of RIXS measurements. The ability to accurately reproduce experimental results from first-principles calculations, without recourse to adjustable parameters, should be viewed as the ultimate test of a proper understanding of the phonon contribution to RIXS.We start by considering only the core-hole--phonon interaction within the context of X-ray photoemission spectroscopy. We combine an ab initio calculation of the real-space response function with many-body Green's functions techniques to reproduce the vibrational side-bands in SiX4 (X=H, F) molecules. The approach we developed is suitable for application to crystalline materials.We next consider the phonon contribution to X-ray absorption spectra. Unlike the charged excitations generated by X-ray photoemission, X-ray absorption creates a neutral excitation that we approximate as a core-hole and an excited electron. We first solved the electronic part of the problem on the level of the Bethe-Salpeter equation and then dressed the resulting 2-particle excitonic quasiparticle with the exciton-phonon interactions using the cumulant ansatz. The viability of this methodology was tested by calculating the N K-edge XAS of the N2 molecule and the O K-edge of acetone. The resulting vibronic spectra agreed favorably with experimental results.Finally, we construct a hybrid formulation of the RIXS cross section that preserves explicit summation over a small number of final states, but replaces the summation over intermediate states, which might be enormously expensive, with a Green's function. We develop an expansion of the Green's function and derive both analytically exact (in the no-recoil limit) and approximate solutions. The formalism was again tested on the O K-edge of acetone and agrees well with the experiment. To provide an outlook towards future work, we discuss application of the developed formalism to crystalline materials

Preisler, Vanessa. "Interaction porteur-phonons dans les boîtes quantiques InAs / GaAs : polarons électroniques et polarons excitoniques." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2006. http://tel.archives-ouvertes.fr/tel-00090546.

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Cette thèse présente une étude des électrons, trous, et excitons confinés dans des boîtes quantiques InAs/GaAs, en prenant en compte leur couplage avec les phonons longitudinaux optiques (LO) du réseau cristallin. Nous montrons que les porteurs confinés dans les boîtes quantiques sont en régime de couplage fort avec ces phonons, et que la conséquence de ce couplage est la formation de particules mixtes porteur-phonon, appelées polarons.

Dans un premier temps, l'interaction électron-phonon ainsi que trou-phonon est étudiée expérimentalement par spectroscopie dans l'infrarouge lointain (50-700 cm-1) sous champ magnétique intense (0-28 T). L'intérêt d'un champ magnétique est de déplacer les transitions électroniques, afin de les amener en résonance avec les phonons, là où les effets du couplage sont le plus évidents. Pour interpréter les résultats expérimentaux, nous avons calculé le couplage entre les états électroniques et les états de phonons LO en utilisant l'Hamiltonien de Fröhlich. On détermine ainsi les états polarons et les forces d'oscillateurs, qui sont en bon accord avec les résultats expérimentaux.

Dans un deuxième temps, nous étudions le couplage des paires électron-trou ou excitons avec les phonons LO. Les transitions interbandes sont sondées dans des expériences de magnetophotoluminescence pour des champs magnétiques allant jusqu'au 28 T. A cause des fluctuations de taille, de composition, et de forme des boîtes quantiques auto-organisées, les pics de photoluminescence sont élargis d'une façon inhomogène. Pour minimiser cet élargissement, des expériences de photoluminescence résonante et d'excitation de la photoluminescence sont effectuées, pour lesquelles un sous-ensemble de boîtes homogènes est sélectionné. Nous calculons les états de polarons excitoniques, ce qui nous permet de déterminer le spectre d'absorption des boîtes quantiques. Un bon accord théorie-expérience est obtenu.

Newton, M. I. N. "Investigation of the interaction between acoustic phonons and the 2DEG of a silicon MOSFET." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380155.

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Mansuripur, Masud. "Light-matter interaction: conversion of optical energy and momentum to mechanical vibrations and phonons." SPIE-INT SOC OPTICAL ENGINEERING, 2016. http://hdl.handle.net/10150/622541.

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Reflection, refraction, and absorption of light by material media are, in general, accompanied by a transfer of optical energy and momentum to the media. Consequently, the eigen-modes of mechanical vibration (phonons) created in the process must distribute the acquired energy and momentum throughout the material medium. However, unlike photons, phonons do not carry momentum. What happens to the material medium in its interactions with light, therefore, requires careful consideration if the conservation laws are to be upheld. The present paper addresses some of the mechanisms by which the electromagnetic momentum of light is carried away by mechanical vibrations.

Lakehal, Massil. "Out of Equilibrium Lattice Dynamics in Pump Probe Setups." Thesis, Université de Paris (2019-....), 2020. http://www.theses.fr/2020UNIP7039.

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L'étude de la dynamique hors équilibre des systèmes fortement corrélés, à l'aide de laser femtoseconde, a révélé une variété de phénomènes sans analogue en physique d'équilibre. Dans cette thèse, nous étudions théoriquement la dynamique hors équilibre des degrés de liberté du réseau et leur signature en spectroscopie pompe-sonde. Nous développons une description microscopique des phonons cohérents displacive excité par le laser. La théorie capture la rétroaction de l'excitation des phonons sur le fluide électronique, qui manque dans la formulation phénoménologique actuelle. Nous montrons que cette rétroaction conduit à une oscillation avec une fréquence qui dépend du temps aux temps courts, même si le mouvement des phonons est harmonique. Pour les temps longs, cette rétroaction apparaît comme une phase résiduelle dans le signal oscillatoire. Nous appliquons la théorie au BaFe2As2, nous expliquons l'origine de la phase du signal oscillatoire rapporté dans des expériences récentes, et nous prédisons que le système oscille avec une fréquence décalé vers le rouge pour les grandes fluences. Notre théorie ouvre également la possibilité d'extraire des informations d'équilibre à partir la dynamique des phonons cohérents. Un autre phénomène intéressant qui a été observé en spectroscopie pompe-sonde est l'oscillation des fluctuations du réseau au double de la fréquence d’un phonon du système étudié. Ces oscillations sont interprétées comme une signature d'états de phonons squeezé macroscopique. Dans ce travail, nous identifions d'autres mécanismes d'oscillations à une fréquence double autre que le squeezing. Nous montrons qu'un quench de la température du bain thermique induite par la pompe, à laquelle le phonon est couplé, ou l'excitation d'un phonon cohérent pour lequel l'anharmonicité cubique est permise par symétrie peut également produire de telles oscillations en spectroscopie sans que le phonon soit dans un état squeezé. Nous concluons que, contrairement à ce qui est communément admis, les oscillations à double fréquence phononique en spectroscopie de bruit ne sont pas nécessairement une signature des phonons squeezés. Nous soulignons ce qui peut être un critère fiable pour identifier un phonon squeezé en utilisant la spectroscopie pompe-sonde
The study of the out of equilibrium dynamics of strongly correlated systems, using ultrafast pulses, uncovered a plethora of phenomena with no analog in equilibrium physics. In this thesis, we theoretically investigate the out of equilibrium dynamics of the lattice degrees of freedom and their signature in pump-probe spectroscopy. We develop a Hamiltonian-based microscopic description of laser pump induced displacive coherent phonons. The theory captures the feedback of the phonon excitation upon the electronic fluid, which is missing in the state-of-the-art phenomenological formulation. We show that this feedback leads to chirping at short timescales, even if the phonon motion is harmonic. At long times, this feedback appears as a finite phase in the oscillatory signal. We apply the theory to BaFe2As2, explain the origin of the phase in the oscillatory signal reported in recent experiments, and we predict that the system will exhibit redshifted chirping at larger fluence. Our theory also opens the possibility to extract equilibrium information from coherent phonon dynamics. Another interesting phenomenon that have been reported in pump-probe spectroscopy is the oscillation of the lattice fluctuations at double phonon frequency. These oscillations are invariably interpreted as a signature of macroscopic squeezed phonon states. In this work, we identify other mechanisms of double phonon frequency oscillations that do not involve squeezing. We show that a pump induced temperature quench of the bath, to which the phonon is coupled to, or exciting a coherent phonon for which cubic anharmonicity is allowed by symmetry can also produce such oscillations in noise spectroscopy without squeezing the phonon state. We conclude that, in contrast with what is commonly believed, double phonon frequency oscillations in noise spectroscopy are not necessarily a signature of macroscopic phonon squeezing. We point out what can be a reliable criterion to identify a squeezed phonon using pump-probe spectroscopy

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Книги з теми "Interaction des phonons":

Nicholas, R. J. The magnetophonon effect. Oxford, England: Pergamon Press, 1985.

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Torres, C. M. Sotomayor, J. P. Leburton, and Jordi Pascual. Phonons in semiconductor nanostructures. Dordrecht: Springer, 1993.

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1949-, Leburton J. P., Pascual Jordi 1949-, Sotomayor Torres C. M, North Atlantic Treaty Organization. Scientific Affairs Division., and NATO Advanced Research Workshop on Phonons in Semiconductor Nanostructures (1992 : San Felíu de Guixols, Spain), eds. Phonons in semiconductor nanostructures. Dordrecht: Kluwer Academic, 1993.

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Shindé, Subhash L., and Gyaneshwar P. Srivastava, eds. Length-Scale Dependent Phonon Interactions. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4614-8651-0.

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Ridley, B. K. Electrons and phonons in semiconductor multilayers. 2nd ed. Cambridge: Cambridge University Press, 2009.

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Ridley, B. K. Electrons and phonons in semiconductor multilayers. Cambridge: Cambridge University Press, 1997.

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Kato, Takashi. Electron-phonon interactions in novel nanoelectronics. New York: Nova Science, 2009.

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Kato, Takashi. Electron-phonon interactions in novel nanoelectronics. New York: Nova Science, 2009.

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1933-, Challis L. J., ed. Electron-phonon interaction in low-dimensional structures. Oxford: Oxford University Press, 2003.

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Aynajian, Pegor. Electron-Phonon Interaction in Conventional and Unconventional Superconductors. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-14968-9.

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Більше джерел

Частини книг з теми "Interaction des phonons":

Dugaev, Vitalii K., and Vladimir I. Litvinov. "Phonons and Electron–Phonon Interaction." In Modern Semiconductor Physics and Device Applications, 101–32. Boca Raton: CRC Press, 2021. http://dx.doi.org/10.1201/9780429285929-6.

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Aynajian, Pegor. "Phonons and Their Interactions." In Electron-Phonon Interaction in Conventional and Unconventional Superconductors, 7–13. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-14968-9_2.

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Efros, Al L. "Electron-Hole Pair — Phonon Interaction in Semiconductor Microcrystals." In Phonons in Semiconductor Nanostructures, 299–308. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1683-1_29.

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Wilkinson, C. D. W. "Engineering Applications of Phonons and the Acousto-Optical Interaction." In Phonons in Semiconductor Nanostructures, 489–97. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1683-1_47.

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Molinari, Elisa. "Phonons and Electron-Phonon Interaction in Low-Dimensional Structures." In Confined Electrons and Photons, 161–203. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4615-1963-8_5.

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Challis, Lawrence J., and Anthony J. Kent. "Acoustic Phonon Interaction with Two-Dimensional Electron and Hole Systems." In Die Kunst of Phonons, 159–87. Boston, MA: Springer US, 1994. http://dx.doi.org/10.1007/978-1-4615-2455-7_17.

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Entin, M. V., and O. V. Kibis. "A Theory op the Suppression of the Electron-Phonon Interaction." In Die Kunst of Phonons, 243–50. Boston, MA: Springer US, 1994. http://dx.doi.org/10.1007/978-1-4615-2455-7_24.

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Hurley, David, Subhash L. Shindé, and Edward S. Piekos. "Interaction of Thermal Phonons with Interfaces." In Topics in Applied Physics, 175–205. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-8651-0_6.

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Brüesch, Peter. "Interaction of X-Rays with Phonons." In Springer Series in Solid-State Sciences, 123–48. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-52263-5_5.

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Shields, A. J., V. A. Haisler, C. Trallero-Giner, and M. Cardona. "Fröhlich Exciton-Phonon Interaction in Quantum Wells: Resonant Raman Spectroscopy under Electric Fields." In Phonons in Semiconductor Nanostructures, 233–41. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1683-1_23.

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Тези доповідей конференцій з теми "Interaction des phonons":

Pop, Eric. "Electron-Phonon Interaction and Joule Heating in Nanostructures." In ASME 2008 3rd Energy Nanotechnology International Conference collocated with the Heat Transfer, Fluids Engineering, and Energy Sustainability Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/enic2008-53050.

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The electron-phonon energy dissipation bottleneck is examined in silicon and carbon nanoscale devices. Monte Carlo simulations of Joule heating are used to investigate the spectrum of phonon emission in bulk and strained silicon. The generated phonon distributions are highly non-uniform in energy and momentum, although they can be approximately grouped into one third acoustic (AC) and two thirds optical phonons (OP) at high electric fields. The phonon dissipation is markedly different in strained silicon at low electric fields, where certain relaxation mechanisms are blocked by scattering selection rules. In very short (∼10 nm) silicon devices, electron and phonon transport is quasi-ballistic, and the heat generation domain is much displaced from the active device region, into the contact electrodes. The electron-phonon bottleneck is more severe in carbon nanotubes, where the optical phonon energy is three times higher than in silicon, and the electron-OP interaction is entirely dominant at high fields. Thus, persistent hot optical phonons are easily generated under Joule heating in single-walled carbon nanotubes suspended between two electrodes, in vacuum. This leads to negative differential conductance at high bias, light emission, and eventual breakdown. Conversely, optical and electrical measurements on such nanotubes can be used to gauge their thermal properties. The hot optical phonon effects appear less pronounced in suspended nanotubes immersed in an ambient gas, suggesting that phonons find relaxation pathways with the vibrational modes of the ambient gas molecules. Finally, hot optical phonons are least pronounced for carbon nanotube devices lying on dielectrics, where the OP modes can couple into the vibrational modes of the substrate. Such measurements and modeling suggest very interesting, non-equilibrium coupling between electrons and phonons in solid-state devices at nanometer length and picoseconds time scales.

Erkılıç, Ufuk, Shengnan Wang, and Yoshitaka Taniyasu. "Exciton-phonon interactions in Janus WSSe." In Conference on Lasers and Electro-Optics/Pacific Rim. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/cleopr.2022.cmp14a_04.

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Interactions of excitons with phonons determine the exciton dynamics in semiconductors. In this work, by investigating temperature dependence of exciton transition energies and linewidths, we revealed enhanced exciton-phonon interaction in monolayer Janus WSSe.

Jin, Jae Sik, and Joon Sik Lee. "Electron-Phonon Interaction Model and Thermal Transport Simulation During ESD Event in NMOS Transistor." In ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32199.

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An electron-phonon interaction model is proposed and applied to the transient thermal transport simulation during electrostatic discharge (ESD) event in the NMOS transistor. The high electron energy induced by the ESD in the transistor is transferred to the lattice phonons through electron-phonon interaction in the local region of the transistor. Due to this fact, a hot spot turns up, the size of which is much smaller than the phonon mean free path in the silicon layer. The full phonon dispersion model based on the Boltzmann transport equation (BTE) with the relaxation time approximation is applied to describe the interactions among different phonon branches and different phonon frequencies. The Joule heating by the electronphonon scattering is modeled through the intervalley and intravalley processes by introducing the average electron energy. In the simulation, the electron-phonon interaction model is used in the hot spot region, and then after a quasi-equilibrium state is achieved there, the temperature of lattice phonons in the silicon is calculated by using the phonon-phonon interaction model. The revolution of peak temperature in the hot spot during the ESD event is simulated and compared to that obtained by the previous full phonon dispersion model which treats the electron-phonon scattering as a volumetric heat source. The results show that the lower group velocity phonon modes (i.e. higher frequency) and optical mode of negligible group velocity obtain the highest energy density from electrons during the ESD event, which induces the devices melting phenomenon. The thermal response of phonon is also investigated, and it is found that the ratio of the phonon group velocity to the phonon specific heat can account for the phonon thermal response. If the ratio is higher than 2, the phonon have a good response to the heat input changes.

Medlar, Michael P., and Edward C. Hensel. "Validation of a Physics Based Three Phonon Scattering Algorithm Implemented in the Statistical Phonon Transport Model." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23307.

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Abstract Three phonon scattering is the primary mechanism by which phonon transport is impeded in insulating and semiconducting bulk materials. Accurate computational modeling of this scattering mechanism is required for high fidelity simulations of thermal transport across the ballistic (quantum mechanics) to Fourier (continuum mechanics) range of behavior. Traditional Monte Carlo simulations of phonon transport use a scaling factor such that each scattering event is considered representative of a large number of phonons, often on the order of 104 physical phonons per simulated event. The ability to account for every phonon scattering event is desirable to enhance model fidelity. A physics-based model using time dependent perturbation theory (Fermi’s Golden Rule) is implemented to compute three phonon scattering rates for each permissible phonon interaction subject to selection rules. The strength of the interaction is based on use of a Gruneisen-like parameter. Both Type I and Type II scattering rates are computed for the allowable interactions that conserve energy and momentum (up to the addition of a reciprocal lattice vector) on a given discretization of momentum space. All of the phonons in the computational domain are represented and phonon populations are updated in momentum space and real space based on the computed number of phonons involved in given scattering events. The computational algorithm is tested in an adiabatic single cell of silicon of dimension 100 × 100 × 100 nm at a nominal temperature of 500 Kelvin containing approximately 108 fully anisotropic phonons. The results indicate that phonon populations return to equilibrium if artificially displaced from that condition. Two approaches are introduced to model the relaxation time of phonon states: the single mode relaxation time (SMRT) which is consistent with the underlying assumptions for previously reported theoretical estimates, and the multi model relaxation time (MMRT) which is more consistent with in-situ conditions. The trends meet physical expectations and are comparable to other literature results. In addition, an estimate of error associated with the relaxation times is presented using the statistical nature of the model. The three phonon scattering model presented provides a high fidelity representation of this physical process that improves the computational prediction of anisotropic phonon transport in the statistical phonon transport model.

Devlen, R. I., J. Kuhl, and K. Ploog. "Plasmon-Phonon Coupling and Hot Carrier Relaxation in GaAs and Low Temperature Grown GaAs." In International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1992. http://dx.doi.org/10.1364/up.1992.mc24.

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Within the first picoseconds after photogeneration, hot carriers in bulk GaAs relax predominantly by emitting optical phonons. The emitted phonons exist as a non-thermal phonon population until they decay anharmonically. Previously, the dynamics of the nonthermal phonon population was studied using time resolved anti-Stokes Raman spectroscopy [1]. For a carrier density larger than 1017 cm−3 the plasma frequency is comparable to the phonon frequency and coupling of the two excitations becomes non-negligible. In GaAs plasmon-phonon coupled modes have been observed in both single component plasmas (via doping)[2] and two component plasmas (via optical excitation)[3]. Due to the interaction of the phonons with the carrier plasma there have been no measurements of the phonon population dynamics for carrier densities larger than about 1017 cm−3. However, these non-equilibrium phonons play an important role in theories of hot carrier relaxation at high densities. In particular the existence of a large non-thermal phonon population and its reabsorption by carriers has been used to explain a reduction in the carrier energy loss rate[4].

Bron, W. E. "Interaction Of Plasma And Optical Phonons In Semiconductors." In 1988 Semiconductor Symposium, edited by Robert R. Alfano. SPIE, 1988. http://dx.doi.org/10.1117/12.947201.

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Demokritov, S. O., A. I. Kirilvuk, N. M. Kreines, V. I. Kudinov, V. B. Smirnov, and M. V. Chetkin. "Interaction between the moving domain wall and phonons." In International Conference on Magnetics. IEEE, 1990. http://dx.doi.org/10.1109/intmag.1990.734948.

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Persans, P. D., and An Tu. "Electron-phonon coupling in II–VI quantum dots." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.wt2.

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The shift in electronic energy levels is the most striking effect when semiconductor particles are reduced in dimension into the quantum dot regime but there are other effects that may also be important in the use of quantum dot materials for nonlinear optics. In this paper we discuss how the interaction between electronic quasiparticles (such as excitons) and phonons is altered as particle dimensions are reduced. Phonons can be confined if the matrix for the quantum dots has no mode at the phonon energy; polaritons may also be quantized. The wavevector of both phonons and electronic quasiparticles is ill-defined to the extend of 1/d, the size of the particle. This uncertainty in wavevector should enhance the coupling between electronic states and phonons.

Naber, W. J. M., T. Fujisawa, H. W. Liu, and W. G. van der Wiel. "Interaction of a 2-level system with 2D phonons." In PHYSICS OF SEMICONDUCTORS: 28th International Conference on the Physics of Semiconductors - ICPS 2006. AIP, 2007. http://dx.doi.org/10.1063/1.2730110.

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Nitsovich, Bohdan M., C. Y. Zenkova, and N. K. Kramar. "Interaction of excitons with optical phonons in layer crystals." In Fifth International Conference on Correlation Optics, edited by Oleg V. Angelsky. SPIE, 2002. http://dx.doi.org/10.1117/12.455210.

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Звіти організацій з теми "Interaction des phonons":

Tajima, T., and T. Taniuti. Nonlinear interaction of photons and phonons in electron-positron plasmas. Office of Scientific and Technical Information (OSTI), March 1990. http://dx.doi.org/10.2172/7055321.

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Sarma, Sankar D. Electron-Phonon Interaction, Transport and Ultrafast Processes in Semiconductor Microstructures. Fort Belvoir, VA: Defense Technical Information Center, August 1992. http://dx.doi.org/10.21236/ada255297.

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Das Sarma, Sankar. Electron-Phonon Interaction, Transport and Ultrafast Processes in Semiconductor Microstructures. Fort Belvoir, VA: Defense Technical Information Center, August 1992. http://dx.doi.org/10.21236/ada255723.

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Chen, R., D. L. Lin, and Thomas F. George. Effects of Electron-Interface-Phonon Interactions on Magnetopolaronic Impurity Transitions in Quantum Wells. Fort Belvoir, VA: Defense Technical Information Center, January 1992. http://dx.doi.org/10.21236/ada244698.

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Favarò, Francesca M. Impact of Smart Phones’ Interaction Modality on Driving Performance for Conventional and Autonomous Vehicles. Mineta Transportation Institute, January 2020. http://dx.doi.org/10.31979/mti.2020.1813.

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Baloch, Imdad, Tom Kaye, Saalim Koomar, and Chris McBurnie. Pakistan Topic Brief: Providing Distance Learning to Hard-to-reach Children. EdTech Hub, June 2020. http://dx.doi.org/10.53832/edtechhub.0026.

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The COVID-19 pandemic has resulted in mass school closures across the world. It is expected that the closures in low- and -middle-income countries (LMICs) will have long-term negative consequences on education and also on broader development outcomes. Countries face a number of obstacles to effectively delivering alternative forms of education. Obstacles include limited experience in facing such challenges, limited teacher digital and pedagogical capacity, and infrastructure constraints related to power and connectivity. Furthermore, inequalities in learning outcomes are expected to widen within LMICs due to the challenges of implementing alternative modes of education in remote, rural or marginalised communities. It is expected that the most marginalised children will feel the most substantial negative impacts on their learning outcomes. Educational technology (EdTech) has been identified as a possible solution to address the acute impact of school closures through its potential to provide distance education. In this light, the DFID Pakistan team requested the EdTech Hub develop a topic brief exploring the use of EdTech to support distance learning in Pakistan. Specifically, the team requested the brief explore ways to provide distance education to children in remote rural areas and urban slums. The DFID team also requested that the EdTech Hub explore the different needs of those who have previously been to school in comparison to those who have never enrolled, with reference to EdTech solutions. In order to address these questions, this brief begins with an overview of the Pakistan education landscape. The second section of the brief explores how four modes of alternative education — TV, interactive radio instruction, mobile phones and online learning — can be used to provide alternative education to marginalised groups in Pakistan. Multimodal distance-learning approaches offer the best means of providing education to heterogeneous, hard-to-reach groups. Identifying various tools that can be deployed to meet the needs of specific population segments is an important part of developing a robust distance-learning approach. With this in mind, this section highlights examples of tools that could be used in Pakistan to support a multimodal approach that reaches the most hard-to-reach learners. The third and final section synthesises the article’s findings, presenting recommendations to inform Pakistan’s COVID-19 education response.<br> <br> This topic brief is available on Google Docs.