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The measured frequencies and intensities of different first- and second- order Raman peaks of suspended graphene are used to show that optical phonons and different acoustic phonon polarizations are driven out of local equilibrium inside a…

Materials Science · Physics 2017-02-22 Sean Sullivan , Ajit Vallabhaneni , Iskandar Kholmanov , Xiulin Ruan , Jayathi Murthy , Li Shi

Step junctions are often present in layered materials, i.e. where single-layer regions meet multi-layer regions, yet their effect on thermal transport is not understood to date. Here, we measure heat flow across graphene junctions (GJs)…

We characterise the dynamics of electrons in twisted bilayer graphene by analysing the time-evolution of electron waves in the atomic lattice. We perform simulations based on a kernel polynomial technique using Chebyshev polynomial; this…

Mesoscale and Nanoscale Physics · Physics 2019-04-24 H. Nam Do , H. Anh Le , D. Bercioux

We present a theoretical study on the electron transmission through the AB-BA stacking boundary in multilayer graphene. Using the tight-binding model and the transfer matrix method, we calculate the electron transmission probability through…

Materials Science · Physics 2015-08-05 Nguyen N. T. Nam , Mikito Koshino

X-ray photoelectron spectroscopy of graphene is important both for its characterization and as a model for other carbon materials. Despite great recent interest, the intrinsic photoemission of its single layer has not been unambiguously…

At high phonon temperature, defect-mediated electron-phonon collisions (supercollisions) in graphene allow for larger energy transfer and faster cooling of hot electrons than the normal, momentum-conserving electron-phonon collisions.…

We study the electron and phonon thermalization in simple metals excited by a laser pulse. The thermalization is investigated numerically by solving the Boltzmann transport equation taking into account all the relevant scattering mechanism:…

Materials Science · Physics 2018-02-28 Shota Ono

Propagating atomic vibrational waves, phonons, rule important thermal, mechanical, optoelectronic and transport characteristics of materials. Thus the knowledge of phonon dispersion, namely the dependence of vibrational energy on momentum…

Materials Science · Physics 2019-10-09 Ryosuke Senga , Kazu Suenaga , Paolo Barone , Shigeyuki Morishita , Francesco Mauri , Thomas Pichler

In graphene, after the electric field is turned-on, the ballistic acceleration of charge carriers up to the monochromatic optic phonon energy generates a back-and-forth motion of the whole distribution function between the zero point energy…

Mesoscale and Nanoscale Physics · Physics 2010-03-04 Samwel K. Sekwao , Jean. P. Leburton

We study the optical conductivity in the low-energy regime of gapped mono- and bilayer graphene. A scaling relation is found, in which the four parameters frequency, gap, Fermi energy and temperature appear only as combination of three…

Materials Science · Physics 2010-01-20 K. Ziegler , A. Sinner

We investigate the scattering of an electron by phonons in a small structure between two one-dimensional tight-binding leads. This model mimics the quantum electron transport through atomic wires or molecular junctions coupled to metallic…

Strongly Correlated Electrons · Physics 2017-02-27 C. Brockt , E. Jeckelmann

The phonon dispersion of graphene on Ir(111) has been determined by means of angle-resolved inelastic electron scattering and density functional calculations. Kohn anomalies of the highest optical-phonon branches are observed at the…

Materials Science · Physics 2015-06-17 M. Endlich , A. Molina-Sánchez , L. Wirtz , J. Kröger

Gapless spectrum of graphene allows easy spatial separation of electrons and holes with an external in-plane electric field. Guided collective plasmon modes can propagate along the separation line, whose amplitude decays with the distance…

Mesoscale and Nanoscale Physics · Physics 2012-05-23 N. M. Hassan , V. V. Mkhitaryan , E. G. Mishchenko

The phonon thermal transport properties of twisted bi-layer graphene are investigated using lattice dynamics and the Boltzmann transport equation. The thermal conductivities of 13.2 and 21.8 twisted configurations are 56% and 36% lower than…

Mesoscale and Nanoscale Physics · Physics 2023-11-07 Shahid Ahmed , Shadab Alam , Ankit Jain

The electron-phonon coupling in ultrafast heating systems is studied within the framework of Boltzmann transport equation (BTE) with coupled electron and phonon transport. A discrete unified gas kinetic scheme is developed to solve the BTE,…

Mesoscale and Nanoscale Physics · Physics 2023-08-25 Chuang Zhang , Rulei Guo , Meng Lian , Junichiro Shiomi

Recent measurements have shown that a continuously tunable bandgap of up to 250 meV can be generated in biased bilayer graphene [Y. Zhang et al., Nature 459, 820 (2009)], opening up pathway for possible graphene-based nanoelectronic and…

Materials Science · Physics 2010-02-11 Cheol-Hwan Park , Steven G. Louie

Identifying the microscopic processes that limit conductivity is essential for understanding correlated and quantum-critical states in quantum materials. In twisted bilayer graphene (TBG) and other twist-controlled materials, the…

For most optoelectronic applications of graphene a thorough understanding of the processes that govern energy relaxation of photoexcited carriers is essential. The ultrafast energy relaxation in graphene occurs through two competing…

We present a new paradigm for understanding optical absorption and hot electron dynamics experiments in graphene. Our analysis pivots on assigning proper importance to phonon assisted indirect processes and bleaching of direct processes. We…

Materials Science · Physics 2017-11-22 Yuan Yang , Grigory Kolesov , Lucas Kocia , Eric J. Heller

We investigate the electronic transport properties of a bilayer graphene flake contacted by two monolayer nanoribbons. Such a finite-size bilayer flake can be built by overlapping two semiinfinite ribbons or by depositing a monolayer flake…

Mesoscale and Nanoscale Physics · Physics 2010-09-23 J. W. Gonzalez , H. Santos , M. Pacheco , L. Chico , L. Brey