DISORDER-INDUCED RELAXATION OF FRENKEL EXCITONS IN MOLECULAR AGGREGATES

A model, based on the intraband scattering of excitons in one-dimensional J-aggregates is proposed to describe the lengthening of the experimentally observed radiative lifetime with temperature. According to this mechanism, the exciton-phonon scattering transfers the oscillator strength fromt he lowest k≅0 optically allowed state to the other states within the excitonic band. A Pauli master equation, in which the hopping rates are calculated, is used to describe the thermalization of the excitonic band. Assuming a fast relaxation mechanism, the temperature dependence of the exciton radiative lifetime is simulated for various chain lengths.

Download Full-text

2D weak anti-localization in thin films of the topological semimetal Pd$$_{3}$$Bi$$_{2}$$S$$_{2}$$

Scientific Reports ◽

10.1038/s41598-021-91930-9 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Shama ◽

R. K. Gopal ◽

Goutam Sheet ◽

Yogesh Singh

Keyword(s):

Thin Films ◽

Phonon Scattering ◽

Surface States ◽

Relaxation Mechanism ◽

Transport Studies ◽

Bulk Carriers ◽

Topological Semimetal ◽

Topological Surface ◽

First Time ◽

Electron Phonon Scattering

AbstractPd$$_{3}$$ 3 Bi$$_{2}$$ 2 S$$_{2}$$ 2 (PBS) is a recently proposed topological semimetal candidate. However, evidence for topological surface states have not yet been revealed in transport measurements due to the large mobility of bulk carriers. We report the growth and magneto-transport studies of PBS thin films where the mobility of the bulk carriers is reduced by two orders of magnitude, revealing for the first time, contributions from the 2-dimensional (2D) topological surface states in the observation of the 2D weak anti-localization (WAL) effect in magnetic field and angle dependent conductivity measurements. The magnetotransport data is analysed within the 2D Hikami-Larkin-Nagaoka (HLN) theory. The analysis suggests that multiple conduction channels contribute to the transport. It is also found that the temperature dependence of the dephasing length can’t be explained only by electron-electron scattering and that electron-phonon scattering also contributes to the phase relaxation mechanism in PBS films.

Download Full-text

Polar Optical Phonon Instability and Intervalley Transfer in Gallium Nitride

MRS Proceedings ◽

10.1557/proc-512-549 ◽

1998 ◽

Vol 512 ◽

Cited By ~ 2

Author(s):

B. E. Foutz ◽

S. K. O'leary ◽

M. S. Shur ◽

L. F. Eastman ◽

B. L. Gelmont ◽

...

Keyword(s):

Gallium Nitride ◽

Analytical Model ◽

Optical Phonon ◽

Room Temperature ◽

Phonon Scattering ◽

Polar Optical Phonon ◽

Scattering Mechanism ◽

Loss Mechanism ◽

One Dimensional ◽

Optical Phonon Scattering

ABSTRACTWe develop a simple, one-dimensional, analytical model, which describes electron transport in gallium nitride. We focus on the polar optical phonon scattering mechanism, as this is the dominant energy loss mechanism at room temperature. Equating the power gained from the field with that lost through scattering, we demonstrate that beyond a critical electric field, 114 kV/cm at T = 300 K, the power gained from the field exceeds that lost due to polar optical phonon scattering. This polar optical phonon instability leads to a dramatic increase in the electron energy, this being responsible for the onset of intervalley transitions. The predictions of our analytical model are compared with those of Monte Carlo simulations, and are found to be in satisfactory agreement.

Download Full-text

Impact of Anharmonic Phonon-Phonon Scattering on Phonon Transport in One-Dimensional System

10.1109/imfedk53601.2021.9637529 ◽

2021 ◽

Author(s):

Atsuya Komada ◽

Nobuya Mori

Keyword(s):

Phonon Scattering ◽

Phonon Transport ◽

Dimensional System ◽

One Dimensional

Download Full-text

Non-coherent diffusion of a vacancy in a one-dimensional lattice in the quasiclassical approximation

Physics and Chemistry of Materials Treatment ◽

10.30791/0015-3214-2021-3-24-29 ◽

2021 ◽

Vol 3 ◽

pp. 24-29

Author(s):

Yu.A. Kashlev ◽

◽

S.A. Maslyaev ◽

Keyword(s):

Phonon Scattering ◽

Nonequilibrium Statistical Mechanics ◽

Tight Binding ◽

Classical Case ◽

Quasiclassical Approximation ◽

Finite Width ◽

Dimensional Lattice ◽

One Dimensional ◽

Temperature Jumps ◽

Two Factors

A vacancy in a one-dimensional lattice is considered as a vacant site in a one-dimensional chain of atoms. The energy model of this system is a double potential well with two levels. Based on the relations of nonequilibrium statistical mechanics, including the Kubo formula for the transport coefficient, the frequency of vacancy jumps is calculated. In this case, two factors of the system perturbation are taken into account: lattice deformation associated with the formation of an empty site, and phonon scattering by mass fluctuations in the chain. An analysis of two high-temperature jumps is given. First, the classical limit of vacancy motion under weak coupling conditions is considered for small values of the gradient of the interaction potential of the defect with the chain. In the classical case, the transition of an atom adjacent to a vacancy occurs through a quasy-stationary excited state. Secondly, a jump under tight binding conditions, when the motion of a neighboring atom occurs through a quasistationary state of finite width, and therefore having a finite lifetime.

Download Full-text