We find that the electronic dispersion in graphite gives rise to double resonant Raman scattering for excitation energies up 5 eV. As we show, curious excitation-energy dependence of D mode is due this process resolving a long-standing problem literature and invalidating recent attempts explain phenomenon. Our calculation D-mode frequency shift ( 60 cm(-1)/eV) agrees well with experimental value.

We report experiments in which picosecond light pulses are used to generate and detect very short stress (coherent longitudinal phonons). present a theory of the generation process, describe how spatial shape pulse is related optical, electronic, acoustical properties material. The detected through measurement changes they induce optical reflectivity sample surface. this effect. experimental results we have obtained for a-${\mathrm{As}}_{2}$${\mathrm{Te}}_{3}$, a-Ge,...

We investigate the tight-binding approximation for dispersion of $\ensuremath{\pi}$ and ${\ensuremath{\pi}}^{*}$ electronic bands in graphene carbon nanotubes. The nearest-neighbor with a fixed ${\ensuremath{\gamma}}_{0}$ applies only to very limited range wave vectors. derive an analytic expression including up third-nearest neighbors. Interaction more distant neighbors qualitatively improves picture, as we show three selected

The Raman-active phonons in orthorhombic perovskitelike ${\mathrm{YMnO}}_{3}$ and ${\mathrm{LaMnO}}_{3}$ were studied by measuring Raman spectra various scattering configurations. experimental line wave numbers the expected shapes for phonon modes compared to those reported other compounds with $\mathrm{Pnma}$ structure results of lattice dynamical calculations. observed lines assigned definite atomic motions. much larger linewidths strong variation increasing laser power case provide...

Using the picosecond pump and probe technique we have detected oscillations of photoinduced transmission reflection in thin films $a$-${\mathrm{As}}_{2}$${\mathrm{Te}}_{3}$ cis-polyacetylene. These are due to generation propagation coherent acoustic phonons film. We discuss detection mechanism, use this effect measure sound velocity a film $a$-Si${\mathrm{O}}_{2}$.

We measured the dispersion of graphite optical phonons in in-plane Brillouin zone by inelastic x-ray scattering. The longitudinal and transverse branches cross along Gamma-K as well Gamma-M direction. was, general, stronger than expected from literature. At K point mode has a minimum is only approximately 70 cm(-1) higher frequency mode. show that first-principles calculations describe very vibrational properties graphene once long-range character dynamical matrix taken into account.

Excitonic effects in the linear and nonlinear optical properties of single-walled carbon nanotubes are manifested by photoluminescence excitation experiments ab initio calculations. One- two-photon spectra showed a series exciton states; their energy splitting is fingerprint excitonic interactions nanotubes. By calculations we determine energies, wave functions, symmetries states. Combining experiment theory find binding energies $0.3--0.4\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ for with...

We study the influence of nitrogen, a potential acceptor in ZnO, on lattice dynamics ZnO. A series samples grown by chemical vapor deposition (CVD) containing different nitrogen concentrations, as determined secondary ion mass spectroscopy (SIMS), was investigated. The Raman spectra revealed vibrational modes at 275, 510, 582, 643, and 856 cm−1 addition to host phonons intensity these additional correlates linearly with concentration can be used quantitative measure These are interpreted...

We present the full in-plane phonon dispersion of graphite obtained from inelastic x-ray scattering, including optical and acoustic branches, as well midfrequency range between $K$ $M$ points in Brillouin zone, where experimental data have been unavailable so far. The existence a Kohn anomaly at point is further supported. fit fifth-nearest neighbor force-constant model to data, making improved calculations both carbon nanotubes available.

From resonant Raman scattering on isolated nanotubes we obtained the optical transition energies, radial breathing mode frequency, and intensity of both metallic semiconducting tubes. We unambiguously assigned chiral index (n(1),n(2)) approximately 50 based solely a third-neighbor tight-binding Kataura plot find omega(RBM)=(214.4+/-2) cm(-1) nm/d+(18.7+/-2) cm(-1). In contrast to luminescence experiments observe all chiralities including zigzag The intensities have systematic chiral-angle...

We present a comprehensive study of the chiral-index assignment carbon nanotubes in aqueous suspensions by resonant Raman scattering radial breathing mode. determine energies first optical transition metallic tubes and second semiconducting for more than 50 chiral indices. The is unique does not depend on empirical parameters. systematics so-called branches Kataura plot are discussed; many properties similar members same branch. show how modes observed single spectrum can be easily assigned...

The anomalous broadening of the ${\mathit{B}}_{1\mathit{g}}$-like phonon R${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ observed in Raman scattering is studied as a function frequency by substituting various rare earths for R. onset starts abruptly at energy which allows us to unambiguously determine single, sharp superconducting gap 2\ensuremath{\Delta}=316 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$....

The five independent elastic moduli of single-crystalline graphite are determined using inelastic x-ray scattering. At room temperature the are, in units GPa, ${C}_{11}=1109$, ${C}_{12}=139$, ${C}_{13}=0$, ${C}_{33}=38.7$, and ${C}_{44}=4.95$. Our experimental results compared with predictions ab initio calculations previously reported incomplete contradictory data sets. We obtain an upper limit $1.1\phantom{\rule{0.3em}{0ex}}\mathrm{TPa}$ for on-axis Young's modulus homogeneous carbon...

We study the electronic structure of ultrathin zinc-blende two-dimensional (2D)-CdSe nanosheets both theoretically, by Hartree-renormalized k·p calculations including Coulomb interaction, and experimentally, temperature-dependent time-resolved photoluminescence measurements. The observed 2D-heavy hole exciton states show a strong influence vertical confinement dielectric screening. A very weak coupling to phonons results in low phonon-contribution homogeneous line-broadening. 2D-nanosheets...

We present a systematic experimental and theoretical study of the two-phonon (2D) Raman scattering in graphene under uniaxial tension. The external perturbation unveils that 2D mode excited with 785 nm has complex line-shape mainly due to contribution two distinct double resonance processes (inner outer) signal. splitting depends on direction applied strain polarization incident light. results give new insight into nature band have significant implications for use as reinforcement composites...

We study the electronic dispersion in chiral and achiral isolated nanotubes as well carbon nanotube bundles. The curvature of wall is found not only to reduce band gap tubes by hybridization, but also alter energies states responsible for transitions visible energy range. Even with larger diameters (1--1.5 nm) a shift levels $\ensuremath{\approx}100 \mathrm{meV}$ obtained our ab initio calculations. Bundling ropes results further decrease semiconducting nanotubes; bundle (10,0) even be...

We present results of second-order Raman-scattering experiments on hexagonal and cubic GaN covering the acoustic optical overtone spectral region. Based a comparison experimental scattering data with calculated phonon-dispersion curves as well group-theoretically derived selection rules, we were able to assign observed structures particular phonon branches determined points in Brillouin zone from which originates. Our measurements reveal energies zone-boundary phonons GaN.

The Raman and infrared phonons of isostructural rhombohedral ${\mathrm{LaMnO}}_{3}$ ${\mathrm{LaAlO}}_{3}$ are studied at room temperature. experimental spectra compared with the prediction lattice-dynamical calculations lines observed assigned to definite atomic vibrations. It is shown that mode ${A}_{1g}$ symmetry in (at $123 {\mathrm{cm}}^{\ensuremath{-}1}$ $236 {\mathrm{cm}}^{\ensuremath{-}1},$ respectively) involves motions cause distortion, i.e., it a ``soft'' mode, its position could...

We present a comprehensive analysis of double-resonant Raman scattering in graphite and derive an analytical expression for the cross section $D$ mode one dimension. The extension to two dimensions does not change phonon wave vectors. In full integration section, contributions by phonons from exactly $K$ point cancel due destructive interference. calculate explicitly based on recent experimental data dispersion. Applying selection rules, mapping additional disorder-induced second-order modes...

We performed density-functional theory calculations in the local-density approximation of structural, electronic, and optical properties 4-$\mathrm{\AA{}}$-diameter single-walled carbon nanotubes. The calculated relaxed geometries show significant deviations from ideal rolled graphene sheet configuration. study effect geometry on electronic band structure finding metallic character (5,0) nanotube to be a consequence high curvature wall. Calculations dielectric function absorption isolated...

We have determined the components of Raman tensor signal-crystal superconducting ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ for phonons at \ensuremath{\sim}500, 440, 330, and 150 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. They all correspond to totally symmetric modes both in tetragonal (${A}_{1g}$) orthorhombic (${A}_{g}$) structures except 330-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ mode which is ${B}_{1g}$ tetragonal....

We report the preparation and investigation of untwinned single-crystal specimens $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$. They were grown from a flux without oxygen annealing treatment, show ${T}_{c}$ 89 K, transition width $\ensuremath{\Delta}{T}_{c}\ensuremath{\approx}3$ an almost complete magnetic shielding effect. The Raman scattering reflects orthorhombic symmetry structure crystals. Furthermore, we found in this crystal that...