TY - JOUR

T1 - Coupled-oscillator model for hybridized optical phonon modes in contacting nanosize particles and quantum dot molecules

AU - Koniakhin, Sergei V.

AU - Utesov, O. I.

AU - Yashenkin, A. G.

PY - 2023/2/27

Y1 - 2023/2/27

N2 - Modification of optical phonon spectra in contacting nonpolar nanoparticles compared to single particlesis studied. Optical phonons in dielectric and semiconducting particles obey the Euclidean metric Klein-FockGordon equation with Dirichlet boundary conditions. This equation is supposed to be solved numerically formanifolds of cojoined spheres. It is proposed to replace this problem with the simpler-to-solve coupled-oscillatormodel (COM), where an oscillator is attributed to each phonon mode of a particle and the particle overlapleads to the appearance of additional couplings for these oscillators with the magnitude proportional to theoverlap volume. For not too big overlaps, this model describes solutions of the original eigenvalue problemwith a quantitative level of accuracy. In particular, it works beyond isotropic s modes in dimers, which has beendemonstrated for p modes in dimers and for tetramers. It is proposed to apply the COM for the descriptionof recently manufactured dimer nanoparticles and quantum dots. The obtained results are in agreement withthe dynamical matrix method for optical phonons in nanodiamonds. The dynamical matrix method is also usedto demonstrate that the van der Waals contacts between faceted particles lead to very small modifications ofthe optical phonon spectra, which therefore could be neglected when discussing the propagation of vibrationalexcitations via a nanopowder. The possibility to distinguish between dimerized and size-distributed singleparticles from their Raman spectra is also considered. The proposed COM paves a way towards the descriptionof propagation of vibrational modes in the ensembles of particles in contact including tight agglomerates,nanocrystal solids, and porous media.

AB - Modification of optical phonon spectra in contacting nonpolar nanoparticles compared to single particlesis studied. Optical phonons in dielectric and semiconducting particles obey the Euclidean metric Klein-FockGordon equation with Dirichlet boundary conditions. This equation is supposed to be solved numerically formanifolds of cojoined spheres. It is proposed to replace this problem with the simpler-to-solve coupled-oscillatormodel (COM), where an oscillator is attributed to each phonon mode of a particle and the particle overlapleads to the appearance of additional couplings for these oscillators with the magnitude proportional to theoverlap volume. For not too big overlaps, this model describes solutions of the original eigenvalue problemwith a quantitative level of accuracy. In particular, it works beyond isotropic s modes in dimers, which has beendemonstrated for p modes in dimers and for tetramers. It is proposed to apply the COM for the descriptionof recently manufactured dimer nanoparticles and quantum dots. The obtained results are in agreement withthe dynamical matrix method for optical phonons in nanodiamonds. The dynamical matrix method is also usedto demonstrate that the van der Waals contacts between faceted particles lead to very small modifications ofthe optical phonon spectra, which therefore could be neglected when discussing the propagation of vibrationalexcitations via a nanopowder. The possibility to distinguish between dimerized and size-distributed singleparticles from their Raman spectra is also considered. The proposed COM paves a way towards the descriptionof propagation of vibrational modes in the ensembles of particles in contact including tight agglomerates,nanocrystal solids, and porous media.

M3 - Article

VL - 5

JO - Physical Review Research

JF - Physical Review Research

SN - 2643-1564

IS - 1

M1 - 013153

ER -