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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 anomalous features of the Raman spectroscopy measurement in MgB$_2$ represent a still unresolved puzzle. In particular highly debated are the origin of the huge $E_{2g}$ phonon linewidth, the nature of the low energy ($\omega <…

Superconductivity · Physics 2009-11-11 E. Cappelluti

We report phonon renormalisation in bilayer graphene as a function of doping. The Raman G peak stiffens and sharpens for both electron and hole doping, as a result of the non-adiabatic Kohn anomaly at the $\Gamma$ point. The bilayer has two…

Mesoscale and Nanoscale Physics · Physics 2015-05-13 A. Das , B. Chakraborty , S. Piscanec , S. Pisana , A. K. Sood , A. C. Ferrari

We present a combined experimental and computational study of two-dimensional molybdenum disulfde (MoS2) and the effect of temperature on the frequency shifts of the Raman-active E2g and A1g modes in the monolayer. While both peaks show an…

The weakly screened electron-hole interactions in an atomically thin semiconductor not only downshift its excitation spectrum from a quasiparticle one, but also redistribute excitation energies and wavefunction characters with profound…

Mesoscale and Nanoscale Physics · Physics 2018-10-24 Yuanxi Wang , Bruno R. Carvalho , Vincent H. Crespi

The vibrational and electronic properties of 2-dimensinal (2D) materials can be efficiently tuned by external strain due to their good stretchability. Resonant Raman spectroscopy is a versatile tool to study the physics of phonons,…

Mesoscale and Nanoscale Physics · Physics 2019-06-05 Chaoyu Song , Fengren Fan , Ningning Xuan , Shenyang Huang , Chong Wang , Guowei Zhang , Fanjie Wang , Qiaoxia Xing , Yuchen Lei , Zhengzong Sun , Hua Wu , Hugen Yan

Using resonant Raman scattering spectroscopy with 25 different laser lines, we describe the Raman scattering spectra of mono- and multi-layers 2H-molybdenum diselenide (MoSe$_2$) as well as the different resonances affecting the most…

Mesoscale and Nanoscale Physics · Physics 2016-04-19 P. Soubelet , A. E. Bruchhausen , A. Fainstein , K. Nogajewski , C. Faugeras

We perform polarization-resolved Raman spectroscopy on graphene in magnetic fields up to 45T. This reveals a filling-factor-dependent, multi-component anticrossing structure of the Raman G peak, resulting from magnetophonon resonances…

Mesoscale and Nanoscale Physics · Physics 2013-06-20 Y. Kim , J. M. Poumirol , A. Lombardo , N. G. Kalugin , T. Georgiou , Y. J. Kim , K. S. Novoselov , A. C. Ferrari , J. Kono , O. Kashuba , V. I. Fal'ko , D. Smirnov

Magneto Raman scattering study of the E$_{2g}$ optical phonons in multi-layer epitaxial graphene grown on a carbon face of SiC are presented. At 4.2K in magnetic field up to 33 T, we observe a series of well pronounced avoided crossings…

Materials Science · Physics 2015-05-13 C. Faugeras , M. Amado , P. Kossacki , M. Orlita , M. Sprinkle , C. Berger , W. A. de Heer , M. Potemski

We investigate the evolution of the Raman spectrum of defected graphene as a function of doping. Polymer electrolyte gating allows us to move the Fermi level up to 0.7eV, as monitored by \textit{in-situ} Hall-effect measurements. For a…

Materials Science · Physics 2014-10-14 M. Bruna , A. K. Ott , M. Ijas , D. Yoon , U. Sassi , A. C. Ferrari

We analyze the effect of electron-phonon coupling on photoemission properties and ultrafast response of doped monolayer MoS2. The analysis is based on combined DFT and many-body (Eliashberg theory) approaches. In particular, we have…

Materials Science · Physics 2015-02-02 Neha Nayyar , Duy Le , Volodymyr Turkowski , Talat S. Rahman

We present low-temperature Raman measurements on gate tunable graphene encapsulated in hexagonal boron nitride, which allows to study in detail the Raman G and 2D mode frequencies and line widths as function of the charge carrier density.…

Mesoscale and Nanoscale Physics · Physics 2023-02-15 Jens Sonntag , Kenji Watanabe , Takashi Taniguchi , Bernd Beschoten , Christoph Stampfer

Insight into why superconductivity in pristine and doped monolayer graphene seems strongly suppressed has been central for the recent years' various creative approaches to realize superconductivity in graphene and graphene-like systems. We…

Superconductivity · Physics 2020-06-12 Even Thingstad , Akashdeep Kamra , Justin W. Wells , Asle Sudbø

Using Raman spectroscopy and transport measurements we investigate thin epitaxial films of Y{1-x}(Pr,Ca)xBa2Cu3O{6+y}. We explore the electronic Raman responses obtained after subtraction of phononic excitations, and the 2Delta peaks that…

Superconductivity · Physics 2017-09-27 A. Bock

Raman spectroscopy has become an essential technique to characterize and investigate graphene and many other two-dimensional materials. However, there still lacks consensus on the Raman signature and phonon dispersion of atomically thin…

We have investigated antidot lattices, which were prepared on exfoliated graphene single layers via electron-beam lithography and ion etching, by means of scanning Raman spectroscopy. The peak positions, peak widths and intensities of the…

Mesoscale and Nanoscale Physics · Physics 2011-07-01 S. Heydrich , M. Hirmer , C. Preis , T. Korn , J. Eroms , D. Weiss , C. Schüller

The use of simple, fast and economic experimental tools to characterize low-dimensional materials is an important step in the process of democratizing the use of such materials in laboratories around the world. Raman spectroscopy has arisen…

We have performed polarized Raman scattering measurements on the newly discovered superconductor Nd(O,F)BiS$_2$ ($T_c = 4$ K). We observe 2 Raman active modes, with frequencies in accordance with first-principles calculations. One A$_{1g}$…

Superconductivity · Physics 2014-09-04 S. F. Wu , P. Richard , X. B. Wang , C. S. Lian , S. M. Nie , J. T. Wang , N. L. Wang , H. Ding

We derive the frequency shifts and the broadening of $\Gamma$ point longitudinal optical (LO) and transverse optical (TO) phonon modes, due to electron-phonon interaction, in graphene under uniaxial strain as a function of the electron…

Mesoscale and Nanoscale Physics · Physics 2015-06-19 Mohamed Assili , Sonia Haddad

Electrostatic gating offers elegant ways to simultaneously strain and dope atomically thin membranes. Here, we report on a detailed \textit{in situ} Raman scattering study on graphene, suspended over a Si/SiO$_2$ substrate. In such a…

Mesoscale and Nanoscale Physics · Physics 2017-01-30 Dominik Metten , Guillaume Froehlicher , Stéphane Berciaud