scholarly journals Phonon group velocity and thermal conduction in superlattices

1999 ◽  
Vol 60 (4) ◽  
pp. 2627-2630 ◽  
Author(s):  
Shin-ichiro Tamura ◽  
Yukihiro Tanaka ◽  
Humphrey J. Maris
Keyword(s):  
Group Velocity ◽  
Thermal Conduction ◽  
Phonon Group Velocity

scholarly journals Heat transport through propagon-phonon interaction in epitaxial amorphous-crystalline multilayers

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Takafumi Ishibe ◽  
Ryo Okuhata ◽  
Tatsuya Kaneko ◽  
Masato Yoshiya ◽  
Seisuke Nakashima ◽  
...  
Keyword(s):  
Group Velocity ◽  
Density Of States ◽  
Heat Dissipation ◽  
Lattice Mismatch ◽  
Lead Telluride ◽  
Amorphous Layer ◽  
Interface Layer ◽  
Phonon Transport ◽  
Nanoscale Systems ◽  
Phonon Group Velocity

AbstractManaging heat dissipation is a necessity for nanoscale electronic devices with high-density interfaces, but despite considerable effort, it has been difficult to establish the phonon transport physics at the interface due to a “complex” interface layer. In contrast, the amorphous/epitaxial interface is expected to have almost no “complex” interface layer due to the lack of lattice mismatch strain and less associated defects. Here, we experimentally observe the extremely-small interface thermal resistance per unit area at the interface of the amorphous-germanium sulfide/epitaxial-lead telluride superlattice (~0.8 ± 4.0 × 10‒9 m2KW−1). Ab initio lattice dynamics calculations demonstrate that high phonon transmission through this interface can be predicted, like electron transport physics, from large vibron-phonon density-of-states overlapping and phonon group velocity similarity between propagon in amorphous layer and “conventional” phonon in crystal. This indicates that controlling phonon (or vibron) density-of-states and phonon group velocity similarity can be a comprehensive guideline to manage heat conduction in nanoscale systems.

Umklapp collisions and thermal conductivity

2021 ◽  
pp. 309-321
Author(s):  
Geoffrey Brooker
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Heat Flow ◽  
Group Velocity ◽  
Thermodynamic Equilibrium ◽  
Reciprocal Lattice ◽  
Reciprocal Lattice Vector ◽  
Momentum Balance ◽  
Lattice Vector ◽  
Phonon Group Velocity

“Umklapp collisions and thermal conductivity” deals with heat conduction in a dielectric solid. Collisions of phonons are divided into Umklapp and normal according as a reciprocal lattice vector is or is not involved in the phonon momentum balance. A local temperature is defined by appeal to local thermodynamic equilibrium. An equilibrium phonon distribution can be off-centred, yet non-decaying, if the only collisions are “normal”, conserving the total phonon momentum. Then heat flow does not decay, even if a representative collision reverses the phonon group velocity. Conversely, in an Umklapp collision it is the non-conservation of phonon momentum that causes heat flow to decay.

THE EFFECT OF SPONTANEOUS AND PIEZOELECTRIC POLARIZATION ON THERMAL CONDUCTIVITY OF InN

2013 ◽  
Vol 27 (09) ◽  
pp. 1350031 ◽  
Author(s):  
BIJAYA KUMAR SAHOO ◽  
SUSANT KUMAR SAHOO ◽  
SUKDEV SAHOO
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Group Velocity ◽  
Room Temperature ◽  
Phonon Scattering ◽  
Polarization Property ◽  
Optical And Electrical Properties ◽  
High Quality ◽  
Phonon Group Velocity ◽  
Debye Frequency

The spontaneous (SP) and piezoelectric (PZ) polarization present in the wurtzite III nitrides influence the optical and electrical properties of these materials. The effects of SP and PZ polarization on thermal properties of III nitrides have yet to be investigated. Here we have investigated the SP and PZ effects on thermal conductivity of InN . Inclusion of polarization property modifies the group velocity of phonons. The combined phonon scattering rates and thermal conductivity k of InN are calculated using modified phonon group velocity, Debye frequency and Debye temperature. Without SP and PZ polarization, the room temperature thermal conductivity of InN is found to be 132.55 W/m.K. Inclusion of SP and PZ polarization property enhances the room temperature thermal conductivity from 132.55 to 134.32 W/m.K. Our predicted thermal conductivity values are closer to the recent experimental value 120 W/m.K measured by Levander et al. for a high quality irradiated InN films at room temperature.

Intensity-dependent phonon group velocity in SiO2 glasses at 0.023 K

1976 ◽  
Vol 57 (5) ◽  
pp. 487-488 ◽  
Author(s):  
J.E. Graebner ◽  
B. Golding
Keyword(s):  
Group Velocity ◽  
Phonon Group Velocity

Lattice Dynamics Study of Anisotropic Heat Conduction in Superlattices

2000 ◽  
Vol 626 ◽  
Author(s):  
B. Yang ◽  
G. Chen
Keyword(s):  
Thermal Conductivity ◽  
Group Velocity ◽  
Lattice Dynamics ◽  
Phonon Scattering ◽  
Diffuse Interface ◽  
Phonon Confinement ◽  
Dynamics Model ◽  
Phonon Group Velocity ◽  
Anisotropic Heat Conduction ◽  
The Cross

ABSTRACTPast studies on the thermal conductivity suggest that phonon confinement and the associated group velocity reduction are the causes of the observed drop in the cross-plane thermal conductivity of semiconductor superlattices. In this work, we investigate the contribution of phonon confinement to the in-plane thermal conductivity of superlattices and the anisotropic effects of phonon confinement on the thermal conductivity in different directions, using a lattice dynamics model. We find that the reduced phonon group velocity due to phonon confinement may account for the dramatic reduction in the cross-plane thermal conductivity, but the in-plane thermal conductivity drop, caused by the reduced group velocity, is much less than the reported experimental results. This suggests that the reduced relaxation time due to diffuse interface phonon scattering, dislocation scattering, etc, should make major contribution to the in-plane thermal conductivity reduction.

Tuning thermal conductivity of crystalline polymer nanofibers by interchain hydrogen bonding

RSC Advances ◽  
2015 ◽  
Vol 5 (107) ◽  
pp. 87981-87986 ◽  
Author(s):  
Lin Zhang ◽  
Morgan Ruesch ◽  
Xiaoliang Zhang ◽  
Zhitong Bai ◽  
Ling Liu
Keyword(s):  
Thermal Conductivity ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Group Velocity ◽  
Thermal Conduction ◽  
Crystalline Polymer ◽  
Polymer Chains ◽  
Torsional Motion ◽  
Polymer Nanofibers

Interchain hydrogen bonds enhance thermal conduction in crystalline polymer nanofibers by confining torsional motion of polymer chains and by increasing the group velocity of phonons.

Reduction of heat capacity and phonon group velocity in silicon nanowires

2015 ◽  
Vol 117 (8) ◽  
pp. 084305 ◽  
Author(s):  
Christopher Marchbanks ◽  
Zhigang Wu
Keyword(s):  
Heat Capacity ◽  
Group Velocity ◽  
Silicon Nanowires ◽  
Phonon Group Velocity

Theory of renormalized phonon group velocity in high-temperature superconductors

2019 ◽  
Vol 33 (27) ◽  
pp. 1950337
Author(s):  
Sanjeev K. Verma ◽  
Anushri Gupta ◽  
Anita Kumari ◽  
B. D. Indu
Keyword(s):  
High Temperature ◽  
Group Velocity ◽  
Quantum Dynamics ◽  
Phonon Frequency ◽  
Phonon Dispersion ◽  
High Temperature Superconductors ◽  
Model Calculations ◽  
Phonon Group Velocity ◽  
Frequency Temperature ◽  
Phonon Dispersion Relations

The expressions for the renormalized phonon group velocity (RPGV) has been developed from renormalized phonon dispersion relations obtained with the help of impurity-induced anharmonic quantum dynamics of phonons via Green’s functions. It is observed that RPGV shows dependence on doping, phonon frequency, temperature, and anharmonicity. The [Formula: see text] superconductor has been taken for model calculations to successfully apply the new results of RPGV.

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