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The femtosecond optical pump-probe technique was used to study dynamics of photoexcited electrons and coherent optical phonons in transition metals Zn and Cd as a function of temperature and excitation level. The optical response in time…

Strongly Correlated Electrons · Physics 2009-11-11 Muneaki Hase , Kunie Ishioka , Jure Demsar , Kiminori Ushida , Masahiro Kitajima

We determine from first-principles the finite-temperature properties--linewidths, line shifts, and lifetimes--of the key vibrational modes that dominate inelastic losses in graphitic materials. In graphite, the phonon linewidth of the…

Materials Science · Physics 2007-10-25 Nicola Bonini , Michele Lazzeri , Nicola Marzari , Francesco Mauri

We study the thermal distribution of intervalley phonons in a graphene sheet. These phonons have two components with the same frequency. The degeneracy of the two modes is preserved by weak electron-phonon coupling. A sufficiently strong…

Materials Science · Physics 2011-07-22 K. Ziegler , E. Kogan

The effect of electron-phonon scattering processes over the thermoelectric properties of extrinsic graphene was studied. Electrical and thermal resistivity, as well as the thermopower, were calculated within the Bloch theory approximations.…

Mesoscale and Nanoscale Physics · Physics 2012-08-02 Enrique Muñoz

The experimental Raman spectra of graphene exhibit a few intense two-phonon bands, which are enhanced through double-resonant scattering processes. Though there are many theoretical papers on this topic, none of them predicts the spectra…

Mesoscale and Nanoscale Physics · Physics 2014-12-17 Valentin N. Popov , Philippe Lambin

In this work we study the behavior of the optical phonon modes in bilayer graphene devices by applying top gate voltage, using Raman scattering. We observe the splitting of the Raman G band as we tune the Fermi level of the sample, which is…

Mesoscale and Nanoscale Physics · Physics 2012-06-07 D. L. Mafra , P. Gava , L. M. Malard , R. S. Borges , G. G. Silva , J. A. Leon , F. Plentz , F. Mauri , M. A. Pimenta

The resistivity of gated graphene is studied taking into account electron and hole scattering by short- and long-range structural imperfections the characteristics of disorder were taken from the scanning tunneling microscopy data and by…

Materials Science · Physics 2007-12-29 F. T. Vasko , V. Ryzhii

The acoustic, optic, and surface polar optic phonons are the three important intrinsic and extrinsic phononic modes that increasingly populate graphene on a substrate with rising temperatures; the coupling of which with photoexcited hot…

Mesoscale and Nanoscale Physics · Physics 2021-12-15 S. Arshia Khatoon , Meenhaz Ansari , S. S. Z. Ashraf , M. Obaidurrahman

We report first-principles calculations of electron-phonon coupling in bilayer graphene and the corresponding contribution to carrier scattering. At the phonon $\Gamma$ point, electrons with energies less than 200 meV are scattered…

Mesoscale and Nanoscale Physics · Physics 2020-07-01 Yijun Ge , Timothy S. Fisher

Using optical-pump terahertz-probe spectroscopy, we study the relaxation dynamics of photoexcited carriers in graphene at different temperatures. We find that at lower temperatures the tail of the relaxation transients as measured by the…

Mesoscale and Nanoscale Physics · Physics 2015-05-30 Jared H. Strait , Haining Wang , Shriram Shivaraman , Virgil B. Shields , Michael G. Spencer , Farhan Rana

Understanding the energy transport by charge carriers and phonons in two-dimensional (2D) van der Waals heterostructures is essential for the development of future energy-efficient 2D nanoelectronics. Here, we performed in situ spatially…

Mesoscale and Nanoscale Physics · Physics 2017-11-21 Daehee Kim , Hanul Kim , Wan Soo Yun , Kenji Watanabe , Takashi Taniguchi , Heesuk Rho , Myung-Ho Bae

We show that the electron-phonon coupling in graphene, in contrast with the non-relativistic two-dimensional electron gas, leads to shifts in the phonon frequencies that are non-trivial functions of the electronic density. These shifts can…

Strongly Correlated Electrons · Physics 2013-05-29 A. H. Castro Neto , Francisco Guinea

This letter calculates the contribution of electron-phonon interaction to thermoelectric effects in graphene. One considers the case of free standing graphene taking into account interaction with intrinsic acoustic phonons. The temperatures…

Mesoscale and Nanoscale Physics · Physics 2015-08-18 S. V. Koniakhin , E. D. Eidelman

Using a combination of ultraviolet-vacuum ultraviolet reflectivity and spectroscopic ellipsometry, we observe a resonant exciton at an unusually high energy of 6.3eV in epitaxial graphene. Surprisingly, the resonant exciton occurs at room…

We examine anharmonic contributions to the optical phonon modes in bulk $T_d$-MoTe$_2$ through temperature-dependent Raman spectroscopy. At temperatures ranging from 100 K to 200 K, we find that all modes redshift linearly with temperature…

Materials Science · Physics 2016-07-20 Jaydeep Joshi , Iris Stone , Ryan Beams , Sergiy Krylyuk , Irina Kalish , Albert Davydov , Patrick Vora

Using electrical transport experiments and shot noise thermometry, we find strong evidence that "supercollision" scattering processes by flexural modes are the dominant electron-phonon energy transfer mechanism in high-quality, suspended…

Mesoscale and Nanoscale Physics · Physics 2015-11-02 Antti Laitinen , Mika Oksanen , Aurélien Fay , Daniel Cox , Matti Tomi , Pauli Virtanen , Pertti Hakonen

We perform a comparative experimental and theoretical study of the temperature dependence up to 700 K of the frequency and linewidths of the graphite E1u and E2g optical phonons (~1590 and 1580 cm-1) by infra-red (IR) and Raman…

Materials Science · Physics 2012-09-21 P. Giura , N. Bonini , G. Creff , J. B. Brubach , P. Roy , M. Lazzeri

Due to its ultra-thin nature, the study of graphene quantum optoelectronics, like gate-dependent graphene Raman properties, is obscured by interactions with substrates and surroundings. For instance, the use of doped silicon with a capping…

The nonequilibrium dynamics of carriers and phonons in graphene is investigated by solving the microscopic kinetic equations with the carrier-phonon and carrier-carrier Coulomb scatterings explicitly included. The Fermi distribution of hot…

Mesoscale and Nanoscale Physics · Physics 2012-03-15 B. Y. Sun , Y. Zhou , M. W. Wu

The role of electron-phonon interactions is experimentally and theoretically investigated near the saddle point absorption peak of graphene. The differential optical transmission spectra of multiple, non-interacting layers of graphene…