We report the ultrafast dynamics of $47.4\phantom{\rule{0.3em}{0ex}}\mathrm{THz}$ coherent phonons graphite interacting with a photoinduced nonequilibrium electron-hole plasma. Unlike conventional materials, upon photoexcitation phonon frequency upshifts, and within few picoseconds relaxes to stationary value. Our first-principles density functional calculations demonstrate that stiffening stems from light-induced decoupling nonadiabatic electron-phonon interaction by creating Time-resolved...

We report the first observation of vibrational Raman spectrum hydrogen molecules ${\mathrm{H}}_{2}$ in crystalline silicon treated with atoms at 400 \ifmmode^\circ\else\textdegree\fi{}C. The observed room temperature exhibits a frequency shift around $4158{\mathrm{cm}}^{\ensuremath{-}1}$ and very broad half-width approximately $34{\mathrm{cm}}^{\ensuremath{-}1}$. An isotope was also detected $2990{\mathrm{cm}}^{\ensuremath{-}1}$ deuterium shifts lines are close agreement those reported for...

Manipulation of the magnetization by external energies other than magnetic field, such as spin-polarized current1-4, electric voltage5,6 and circularly polarized light7-11 gives a paradigm shift in nanodevices. Magnetization control ferromagnetic materials only light has received increasing attention both fundamental probe interactions magnetism but also for future high-density recording technologies. Here we show that granular FePt films, designed ultrahigh-density recording, optical...

The femtosecond optical pump-probe technique was used to study dynamics of photoexcited electrons and coherent phonons in transition metals Zn Cd as a function temperature excitation level. response time domain is well fitted by linear combination damped harmonic oscillation because ${E}_{2g}$ phonon subpicosecond transient due electron-phonon thermalization. thermalization monotonically increases with temperature, consistent the thermomodulation scenario, where at high temperatures system...

We have studied the ${A}_{1g}$ coherent phonons in bismuth generated by high fluence ultrashort laser pulses. observed that nonlinear regime, where phonons' oscillation parameters depend on fluence, consists of subregimes with distinct dynamics. Just after entering become chirped. Increasing further leads to emergence a collapse and revival, which next turns into multiple collapses revivals. This is explained dynamics wave packet an anharmonic potential, periodically breaks up reconstitutes...

The authors report femtosecond dynamics of the coherent optical phonon single crystal diamond. Sub-10fs, 395nm laser pulses excite 40THz phonons with an extremely small damping rate (0.15ps−1). Linear power dependence amplitude under off-resonant excitation condition gives a direct evidence for eletric-field-driven generation mechanism. is noticeably suppressed by doping nitrogen impurities, in spite their absorption near ultraviolet. present study demonstrates that simple pump-probe...

Abstract In a bulk solid, optical control of atomic motion provides better understanding its physical properties and functionalities. Such studies would benefit from active visualization motions in arbitrary directions, yet, so far, mostly only one-dimensional has been shown. Here we demonstrate novel method to optically visualize two-dimensional solid. We use femtosecond laser pulse coherently superpose two orthogonal crystalline bismuth. The relative amplitudes those are manipulated by...

The concentration dependence of optical phonons in the ${\mathrm{TiO}}_{2}$-${\mathrm{SnO}}_{2}$ system whose phase diagram exhibits a miscibility gap, has been studied by Raman scattering and Fourier-transform infrared spectroscopy. X-ray diffraction confirmed that mixed oxides ${\mathrm{Ti}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sn}}_{\mathit{x}}$${\mathrm{O}}_{2}$ with intervals x=0.1 are single uniform (tetragonal) except some x's; no separation spinodal decomposition could be...

Excited state electron transfer at the adsorbate/metal interface represents a key step in molecular electronic devices. The dynamics of such processes are governed by ultrafast energy relaxation which can be probed directly time-resolved two-photon photoemission (2PPE). Using 2PPE spectroscopy we investigate energetics and lifetimes unoccupied states C6F6 adsorbed on Cu(111) as model system for organic/metal interfaces. With increasing layer thickness find pronounced decrease energetic...

Bismuth has been a model material in the study of femtosecond dynamics coherent lattice oscillations. The generation mechanism was first proposed to be displacive for symmetric A1g mode, which only mode observed as phonon. absence other Raman active Eg not fully explained, but phenomenologically attributed exclusive coupling hot electrons at k∼0 and high symmetry phonons. In present study, we demonstrate that both modes are excited phonons low temperature confirm generated via process...

We report the ultrafast dynamics of coherent A1g and Eg phonons antimony as a function temperature optical polarization. Like in bismuth, two phonon modes exhibit nearly π/2 difference their initial phase, suggesting different coupling strengths with photoexcited electrons. The dependence amplitude on polarization indicates generation through both displacive Raman processes, rather than purely one. In contrast, can be understood within framework alone.

By time-resolved reflectivity measurements with sub-10 fs laser pulses at 395 nm, the coherent phonons of aligned bundles single-walled carbon nanotubes are observed for various polarization directions pump and probe pulses. In isotropic measurement, we observe radial breathing modes, G, even D while in anisotropic mode, only G mode appears. A complex dependence band phonon amplitude is explained by superposition different symmetries.

Efficient charge separation at the interfaces between perovskite and with carrier transport layers is crucial for solar cells to achieve high power conversion efficiency. We systematically investigate hole injection dynamics from MAPbI$_3$ three typical materials (HTMs) PEDOT:PSS, PTAA NiO$_x$ by means of pump-probe transmission measurements. photoexcite only near MAPbI$_3$/HTM interface or back surface, measure differential transient two excitation configurations extract directly related...

The ultrafast coupling dynamics of coherent optical phonons and the photoexcited electron-hole plasma in indirect gap semiconductor GaP are investigated by experiment theory. For below-gap excitation probing 800-nm light, only bare longitudinal (LO) observed. above-gap with 400-nm photoexcitation creates a high density, nonequilibrium $e\text{\ensuremath{-}}h$ plasma, which introduces an additional, faster decaying oscillation due to LO phonon-plasmon coupled (LOPC) mode. LOPC mode frequency...

We have studied the effect of point defects on coherent optical phonons in ion-implanted bismuth polycrystalline films. Ultrafast dynamics and photogenerated carriers femtosecond time domain been investigated by means pump-probe reflectivity measurements. The dephasing rate A1g phonon increases linearly with increasing ion dose, which is explained additional process originated from scattering defects. Carrier are also found to be affected mediated

We have found that hydrogen exists in molecular form crystalline silicon treated with atoms the downstream of a plasma. The vibrational Raman line molecules is observed at $4158{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ for samples hydrogenated between 180 and 500 \ifmmode^\circ\else\textdegree\fi{}C. assignment confirmed by its isotope shift to $2990{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ deuterium atoms. intensity has maximum hydrogenation 400 broad asymmetric. It consists least two...

Detection mechanisms of coherent phonons in variously doped GaAs are investigated by transient reflectivity method with photoexcitation near the ${E}_{0}$ gap and probe either or ${E}_{1}$ gaps. By varying light polarization angle, amplitudes both LO phonon phonon-plasmon coupled (LOPC) modes show evidence for an interference between their anisotropic isotropic dielectric response components. We attribute components to modulation lattice electronic polarizations via dipole-allowed...

We report on the intrinsic optical generation and detection of coherent acoustic phonons at (001)-oriented bulk Si GaP without metallic phonon transducer structures. Photoexcitation by a 3.1-eV laser pulse generates normal strain within $\ensuremath{\sim}100$-nm penetration depth in both semiconductors. The subsequent propagation into is detected with delayed probe as periodic modulation reflectivity. Our theoretical model explains quantitatively via deformation potential electron-phonon...

We demonstrate an all-optical approach to probe electronic band structure at buried interfaces involving polar semiconductors. Femtosecond optical pulses excite coherent phonons in epitaxial GaP films grown on Si(001) substrate. find that the phonon amplitude critically depends film growth conditions, specifically presence of antiphase domains, which are independently characterized by transmission electron microscopy. determine Fermi levels interface GaP/Si from amplitudes and internal...

Abstract Ultrafast charge‐carrier and phonon dynamics at the buried heterointerface of GaP/Si(001) are investigated by means two‐color pump‐probe reflectivity measurements. The carrier‐induced signal exhibits a resonant enhancement pump‐photon energy 1.4 eV, which is assigned to an optical transition interface. In addition, transient modulated coherent oscillation 2 THz, whose amplitude also becomes maximum eV. observed behavior oscillation, in combination with characteristic...

We report the ultrafast dynamics of simultaneously excited coherent A1g and Eg phonons in semimetals Bi Sb. At a low level excitation, doubly degenerate pump–probe data occur at temperature only, they nearly vanish room temperature. Their initial phase is shifted by π/2 with respect to that fully symmetric indicating are predominantly impulsively displacively, respectively. high both display an asymmetric (varying time) line shape more spectral weight frequencies testifying quantum...