The Holstein Hubbard and Holstein t–J models are studied for a wide range of phonon frequencies, electron–electron and electron–phonon interaction strengths on finite lattices with up to ten sites by means of direct Lanczos diagonalization. Previously the necessary truncation of the phononic Hilbert space caused serious limitations to either very small systems (four or even two sites) or to wea...

The properties of iron under extreme conditions are intensively studied [1] due to its relevance for geophysical models of the earth’s interior. From a more general point of view, the behaviour of bcc iron under compression is interesting since almost half of the elements contain the bcc structure in their phase diagram. The phonon dispersion of bcc elements was studied in the past in search of...

We simulate phonon transport in suspended graphene nanoribbons (GNRs) with real-space edges and experimentally-relevant widths and lengths (from submicron to hundreds of microns). The full-dispersion phonon Monte Carlo (PMC) simulation technique, which we describe in detail, involves a stochastic solution to the phonon Boltzmann transport equation with the relevant scattering mechanisms (edge, ...

Lattice thermal conductivity of a quantum well limited by umklapp, impurity, and boundary scattering was investigated theoretically by taking into account dispersion of confined acoustic-phonon modes. We show that strong modification of phonon group velocities due to spatial confinement leads to a significant increase in the phonon relaxation rates. From the numerical calculations, we predict a...

The present work reports a study of the structural, elastic, dynamical and thermodynamic properties of rock salt (RS) LiCl within density functional theory. It is found that the lattice constant and elastic constants are in very good agreement with the other calculations or experimental values. The phonon dispersion curve along several high symmetry lines at the Brillouin zone (BZ) is determine...

We have studied the trigonal warping effect in metallic carbon nanotubes using resonance Raman scattering and examining the G0-band profile for individual metallic single-wall carbon nanotubes. We show that the observed splitting in the G0-band phonon spectra is directly correlated with the splitting in the singularities of the joint density of electronic states, i.e., detailed information abou...

The method to obtain phonon dispersion of achiral single-wall carbon nanotubes (SWNTs) from 6× 6 matrix proposed by Mahan and Jeon has been extended to chiral SWNTs. The number of calculated phonon modes of a chiral SWNT (10, 1) is much larger than that of a zigzag one (10, 0) because the number of atoms in the translational unit cell of chiral SWNT is larger than that of an achiral one even th...

A quantum theory of dispersion for an inhomogeneous solid is obtained, from a starting point of multipolar coupled atoms interacting with an electromagnetic field. The dispersion relations obtained are equivalent to the standard classical Sellmeir equations obtained from the Drude-Lorentz model. In the homogeneous ~planewave! case, we obtain the detailed quantum mode structure of the coupled po...

The phonon dispersion and the electron-phonon interaction for the β-Po and the bcc high pressure phases of tellurium are computed with densityfunctional perturbation theory. Our calculations reproduce and explain the experimentally observed pressure dependence of the superconducting critical temperature (Tc) and confirm the connection between the jump in Tc and the structural phase transition. ...

We demonstrate the confinement of acoustic phonons in ultrathin silicon layers and study its effect on electron mobility. We develop a model for confined acoustic phonons in an ideal single-layer structure and in a more realistic three-layer structure. Phonon quantization is recovered, and the dispersion relations for distinct phonon modes are computed. This allows us to obtain the confined pho...