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Phonon Coupling (phonon + coupling)

Distribution by Scientific Domains

Physics and Astronomy	40%
Chemistry	40%
Polymers and Materials Science	20%

Selected Abstracts

Revealing the Electron,Phonon Coupling in a Conjugated Polymer by Single-Molecule Spectroscopy,

ADVANCED MATERIALS, Issue 15 2007
R. Hildner
Electron,phonon coupling in a ,-conjugated polymer is revealed by single-molecule spectroscopy in combination with statistical pattern recognition techniques. The technique allows to reveal the phonon-side band in the spectra of methyl-substituted ladder-type poly(para-phenylene) (see figure). For this polymer a weak electron,phonon coupling strength is found at low temperatures. The distribution of the phonon frequencies provides strong evidence that the low-energy vibrational modes, which couple to the electronic transitions, stem from vibrations of the host matrix. [source]

Topotactic Intercalation of a Metallic Dense Host Matrix Chalcogenide with Large Electron,Phonon Coupling: Crystal Structures and Electronic Properties of LixMo2SbS2 (0 , x , 0.7).

CHEMINFORM, Issue 15 2007
Alexandros Lappas
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Single-Molecule Spectroscopy on a Ladder-Type Conjugated Polymer: Electron,Phonon Coupling and Spectral Diffusion

CHEMPHYSCHEM, Issue 14 2009
Richard Hildner Dr.
Abstract We employ low-temperature single-molecule spectroscopy combined with pattern recognition techniques for data analysis on a methyl-substituted ladder-type poly(para -phenylene) (MeLPPP) to investigate the electron,phonon coupling to low-energy vibrational modes as well as the origin of the strong spectral diffusion processes observed for this conjugated polymer. The results indicate weak electron,phonon coupling to low-frequency vibrations of the surrounding matrix of the chromophores, and that low-energy intrachain vibrations of the conjugated backbone do not couple to the electronic transitions of MeLPPP at low temperatures. Furthermore, these findings suggest that the main line-broadening mechanism of the zero-phonon lines of MeLPPP is fast, unresolved spectral diffusion, which arises from conformational fluctuations of the side groups attached to the MeLPPP backbone as well as of the surrounding host material. [source]

Interfacial Polar-Bonding-Induced Multifunctionality of Nano-Silicon in Mesoporous Silica

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009
Jung Y. Huang
Abstract The optoelectronic response of a material governs its suitability for a wide range of applications, from photon detection to photovoltaic conversion. To conquer the material limitations and achieve improved optoelectronic responses, nanotechnology has been employed to arrange subunits with specific size-dependent quantum mechanical properties in a hierarchically organized structure. However, building a functional optoelectronic system from nano-objects remains a formidable challenge. In this paper, the fabrication of a new artificially engineered optoelectronic material by the preferential growth of silicon nanocrystals on the bottom of the pore-channels of mesoporous silica is reported. The nanocrystals form highly stable interface structures bonded on one side; these structure show strong electron,phonon coupling and a ferroelectric-like hysteretic switching property. A new class of multifunctional materials is realized by invoking a concept that employs semiconductor nanocrystals for optical sensing and utilizes interfacial polar layers to facilitate carrier transport and emulate ferroelectric-like switching. [source]

Davydov's solitons in zigzag carbon nanotubes

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2010
Larissa Brizhik
Abstract Nonlinear mechanism of charge transport in low-dimensional nanosystems is considered, based on the account of the electron,phonon interaction that arises from the deformation dependencies of the on-site and the hopping interaction energies at intermediatevalues of the corresponding coupling constants. In particular, carbon-type hexagonal zigzag nanotubes are studied. It is shown that in the adiabatic approximation the electron,phonon coupling results in the self-trapping of carriers and formation of polaron (soliton) states. We show that the ground state of an electron in a nanotube is a low-dimensional polaron whose symmetry depends on the strength of the coupling. Namely, at relatively weak coupling, the polaron possesses quasi-one-dimensional properties and has an azimuthal symmetry. When the coupling constant exceeds some critical value, the azimuthal symmetry breaks down and two-dimensional polaron on the nanotube surface is formed. There are also polarons formed by the electrons in the conducting band (or by holes in the valence band) in semiconducting zigzag carbon nanotubes. Such polarons are described by the system of coupled nonlinear Schroedinger equations which admits single-band polarons, and entangled (hybridized) polarons. These two types of polarons possess different energies and symmetry properties. Single-band solutions are one-dimensional polarons: they are azimuthally symmetric and localized along the nanotube axis. The entangled polarons are also self-trapped along the nanotube axis, but possess an inner structure and are modulated around the nanotube. The entangled polarons break the azimuthal symmetry and their energy is lower than the energy of single-band polarons. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source]

First and second optical transitions in single-walled carbon nanotubes: a resonant Raman study

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11 2007
H. Telg
Abstract Resonant Raman spectroscopy was performed to study electron,phonon coupling in single-walled carbon nanotubes separated in solution. By varying the excitation energy from 1.26 eV to 1.93 eV we obtained radial breathing mode resonance profiles of the first and second optical transitions E11 and E22 of the (9,1) and (8,3) tubes. We observe up to 16 times stronger Raman intensities for the E11 transitions which can mostly be attributed to a two times broader linewidth of the E22 transition. Comparison of the matrix element ratio ,11/,22 to theoretical predictions on the electron,phonon coupling show a deviation of a factor 1.7 which might be associated with the change of the exciton,photon matrix element. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Nonlocal electron,phonon coupling: influence on the nature of polarons

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2004
V. M. Stojanovi
Abstract We present a variational approach to an extended Holstein model, comprising both local and nonlocal electron,phonon coupling. The approach is based on the minimization of a Bogoliubov bound to the free energy of the coupled electron-phonon system, and is implemented for a one-dimensional nearest-neighbor model, with Einstein phonons. The ambivalent character of nonlocal coupling, which both promotes and hinders transport, is clearly observed. A salient feature of our results is that the local and nonlocal couplings can compensate each other, leading to a supression of polaronic effects. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Mechanisms of exciton spin relaxation in quantum dots

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2003
E. Tsitsishvili
Abstract We study the phonon-assisted relaxation processes (longitudinal relaxation time T1) within the radiative doublet of the heavy-hole-exciton in asymmetrical quantum dots. Two different relaxation mechanisms are considered: the exciton spin,acoustic phonon coupling via the strain-dependent short-range exchange interaction and the second-order quasielastic interaction between charge carriers and LO phonons. For zero magnetic fields and low temperatures, the calculated relaxation times for typical QDs are very long compared to the exciton lifetime yet they are strongly reduced in high magnetic fields (of the order of a few Tesla) and high temperatures T , 100 K. [source]