Study of Transient Phonon Dynamics
Study of Transient Phonon Dynamics

Author: W. E. Bron

Publisher:

Published: 1986

Total Pages: 16

ISBN-13:

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The research program during the past three year grant period has been quite successful in devising new, and adapting existing, laser based techniques to the study of short and ultra-short duration laser induced transient dynamics. For the most part, work has concentrated on the dynamics of excited, nonequilibrium phonon distributions in semiconductors and in ionic solids. The excitation brings the solids well away from thermal equilibrium. It has been the author's contention that phonon dynamics and phonon transport can be investigated in greater detail by nonequilibrium techniques than by thermal equilibrium techniques as, e.g., thermal conductivity measurements. The results obtained so far offer an excellent opportunity for the expansion of existing methods and facilities to new areas of research. Keywords: Transient Phonon Dynamics; Lasers; Ionic Solids; Phonon Dynamics; and Phonon Transport.

Nonequilibrium Phonon Dynamics
Nonequilibrium Phonon Dynamics

Author: Walter E. Bron

Publisher: Springer Science & Business Media

Published: 2013-11-11

Total Pages: 682

ISBN-13: 1461325013

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Phonons are always present in the solid state even at an absolute temperature of 0 K where zero point vibrations still abound. Moreover, phonons interact with all other excitations of the solid state and, thereby, influence most of its properties. Historically experimental information on phonon transport came from measurements of thermal conductivity. Over the past two decades much more, and much more detailed, information on phonon transport and on many of the inherent phonon interaction processes have come to light from experiments which use nonequilibrium phonons to study their dynamics. The resultant research field has most recently blossomed with the development of ever more sophisticated experimental and theoretical methods which can be applied to it. In fact, the field is moving so rapidly that new members of the research community have difficulties in keeping up to date. This NATO Advanced Study Institute (ASI) was organized with the objective of overcoming the information barrier between those expert in the field and those who are new to it. Thus it was decided to (i) organize a set of tutorially based lectures covering most of the important facets in the field, and (ii) to produce an Institute proceedings which would serve both as the first general textbook, as well as a valuable reference book, for this field of knowledge.

Research in Progress
Research in Progress

Author: United States. Army Research Office

Publisher:

Published: 1984

Total Pages: 284

ISBN-13:

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Vols. for 1977- consist of two parts: Chemistry, biological sciences, engineering sciences, metallurgy and materials science (issued in the spring); and Physics, electronics, mathematics, geosciences (issued in the fall).

Ultrafast Dynamical Processes in Semiconductors
Ultrafast Dynamical Processes in Semiconductors

Author: Kong-Thon Tsen

Publisher: Springer Science & Business Media

Published: 2004-02-25

Total Pages: 424

ISBN-13: 9783540402398

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An international team of experts describes the optical and electronic properties of semiconductors and semiconductor nanostructures at picosecond and femtosecond time scales. The contributions cover the latest research on a wide range of topics. In particular they include novel experimental techniques for studying and characterizing nanostructure materials. The contributions are written in a tutorial way so that not only researchers in the field but also researchers and graduate students outside the field can benefit.

Phonon Hydrodynamic Transport at Elevated Temperature
Phonon Hydrodynamic Transport at Elevated Temperature

Author: Zhiwei Ding

Publisher:

Published: 2021

Total Pages: 0

ISBN-13:

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For over half a century, phonon hydrodynamic transport was deemed exotic and mattered only at extremely low temperatures. In this work, by combining the theoretical and experimental approach, we successfully predict and confirm the existence of phonon hydrodynamic transport in graphite above 200 K. More specifically, we introduce a direction-dependent definition of normal and Umklapp scattering, which gives an improved description of mode-specific phonon dynamics. By extending the classical Fuchs-Sondheimer solution, we developed a first-principles framework to study phonon hydrodynamics under the size effect with mode-by-mode phonon scattering details. We unambiguously revealed the Poiseuille heat flow by studying the variation of heat flow as the graphite ribbon width and identified for the first time the existence of phonon Knudsen minimum -- an unusual phenomenon unique to hydrodynamic regime -- which can be observed up to 90 K. Using a sub-picosecond transient grating technique, we directly observed second sound in graphite at record-high temperatures of 200 K. With the enlarged grating-period window, we firstly reported the dispersion of thermal wave, whose velocity increases with decreasing grating period. Our experimental findings are well explained with the interplay among "three fluids": ballistic, diffusive, and hydrodynamic phonons. We believe our study may stimulate further work into discovering more material systems possessing significant phonon hydrodynamic features, as well as new research into understanding and manipulating the phonon transport in the hydrodynamic scheme.

Phonon Physics The Cutting Edge
Phonon Physics The Cutting Edge

Author:

Publisher: Elsevier

Published: 1995-12-13

Total Pages: 543

ISBN-13: 0080538789

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The first two volumes in this series published twenty years ago contained chapters devoted to anharmonic properties of solids, ab initio calculations of phonons in metals and insulators, and surface phonons. In the intervening years each of these important areas of lattice dynamics has undergone significant developments. This volume is therefore concerned with reviewing the current status of these areas.Chapter one deals with the path-integral quantum Monte-Carlo method as a numerical simulation approach and looks at how this has been applied successfully to the determination of low temperature thermodynamic properties of anharmonic crystals and to certain dynamical properties as well. Chapter two is concerned with the calculation of static and dynamic properties of anharmonic crystals in the quantum regime. Chapter three discusses intrinsic anharmonic localized modes that have been intensively studied recently. Two topics, ab initio calculations of phonons in metals, and surface phonons are dealt with in the next chapter. The remaining two chapters are devoted to topics that have not been treated in previous volumes. One is phonon transport and the second is phonons in disordered crystals.The work described in the six chapters of this volume testifies to the continuing vitality of the field of dynamical properties of solids nearly a century after its founding.

Ultrafast Dynamics of Electrons and Phonons in Graphitic Materials
Ultrafast Dynamics of Electrons and Phonons in Graphitic Materials

Author:

Publisher:

Published: 2009

Total Pages:

ISBN-13:

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This work focuses on the ultrafast dynamics of electrons and phonons in graphitic materials. In particular, we experimentally investigated the factors which influence the transport properties of graphite and carbon nanotubes. In the first part of this dissertation, we used Time-resolved Two Photon photoemission (TR-TPP) spectroscopy to probe the dynamics of optically excited charge carriers above the Fermi energy of double-wall carbon nanotubes (DWNTs). In the second part of this study, time-resolved anti-Stokes Raman (ASR) spectroscopy is applied to investigating in real time the phonon-phonon interactions, and addressing the way the temperature affects the dynamics of single-wall carbon nanotubes (SWNTs) and graphite. With respect to the first part, we aim to deeply understand the dynamics of the charge carriers and electron-phonon interactions, in order to achieve an as complete as possible knowledge of DWNTs. We measured the energy transfer rate from the electronic system to the lattice, and we observed a strong non-linear increase with the temperature of the electrons. In addition, we determined the electron-phonon coupling parameter, and the mean-free path of the electrons. The TR-TPP technique enables us to measure the above quantities without any electrical contacts, with the advantage of reducing the errors introduced by the metallic electrodes. The second investigation uses time-resolved ASR spectroscopy to probe in real time the G-mode non-equilibrium phonon dynamics and the energy relaxation paths towards the lattice by variation of the temperature in SWNTs and graphite. The lifetime range of the optically excited phonons obtained is 1.23 ps to 0.70 ps in the lowest (cryogenic temperatures) and highest temperature limits, respectively. We have also observed an increase in the energy of the G-mode optical phonons in graphite with the transient temperature. The findings of this study are important since the non-equilibrium phonon population has been invoked to explain the negative differential conductance and current saturation in high biased transport phenomena.

The Physics of Phonons
The Physics of Phonons

Author: Gyaneshwar P. Srivastava

Publisher: Routledge

Published: 2019-07-16

Total Pages: 438

ISBN-13: 1351409557

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There have been few books devoted to the study of phonons, a major area of condensed matter physics. The Physics of Phonons is a comprehensive theoretical discussion of the most important topics, including some topics not previously presented in book form. Although primarily theoretical in approach, the author refers to experimental results wherever possible, ensuring an ideal book for both experimental and theoretical researchers. The author begins with an introduction to crystal symmetry and continues with a discussion of lattice dynamics in the harmonic approximation, including the traditional phenomenological approach and the more recent ab initio approach, detailed for the first time in this book. A discussion of anharmonicity is followed by the theory of lattice thermal conductivity, presented at a level far beyond that available in any other book. The chapter on phonon interactions is likewise more comprehensive than any similar discussion elsewhere. The sections on phonons in superlattices, impure and mixed crystals, quasicrystals, phonon spectroscopy, Kapitza resistance, and quantum evaporation also contain material appearing in book form for the first time. The book is complemented by numerous diagrams that aid understanding and is comprehensively referenced for further study. With its unprecedented wide coverage of the field, The Physics of Phonons will be indispensable to all postgraduates, advanced undergraduates, and researchers working on condensed matter physics.