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Title: Ultrafast and nanoscale plasmonic phenomena in exfoliated graphene revealed by infrared pump-probe nanoscopy
Authors: Wagner, M.
Fei, Z.
McLeod, A.S.
Rodin, A.S.
Bao, W.
Iwinski, E.G.
Zhao, Z.
Goldflam, M.
Liu, M.
Dominguez, G.
Thiemens, M.
Fogler, M.M.
Castro Neto, A.H. 
Lau, C.N.
Amarie, S.
Keilmann, F.
Basov, D.N.
Keywords: Dirac plasmon
near-field microscopy
time-resolved spectroscopy
Issue Date: 12-Feb-2014
Citation: Wagner, M., Fei, Z., McLeod, A.S., Rodin, A.S., Bao, W., Iwinski, E.G., Zhao, Z., Goldflam, M., Liu, M., Dominguez, G., Thiemens, M., Fogler, M.M., Castro Neto, A.H., Lau, C.N., Amarie, S., Keilmann, F., Basov, D.N. (2014-02-12). Ultrafast and nanoscale plasmonic phenomena in exfoliated graphene revealed by infrared pump-probe nanoscopy. Nano Letters 14 (2) : 894-900. ScholarBank@NUS Repository.
Abstract: Pump-probe spectroscopy is central for exploring ultrafast dynamics of fundamental excitations, collective modes, and energy transfer processes. Typically carried out using conventional diffraction-limited optics, pump-probe experiments inherently average over local chemical, compositional, and electronic inhomogeneities. Here, we circumvent this deficiency and introduce pump-probe infrared spectroscopy with ∼20 nm spatial resolution, far below the diffraction limit, which is accomplished using a scattering scanning near-field optical microscope (s-SNOM). This technique allows us to investigate exfoliated graphene single-layers on SiO2 at technologically significant mid-infrared (MIR) frequencies where the local optical conductivity becomes experimentally accessible through the excitation of surface plasmons via the s-SNOM tip. Optical pumping at near-infrared (NIR) frequencies prompts distinct changes in the plasmonic behavior on 200 fs time scales. The origin of the pump-induced, enhanced plasmonic response is identified as an increase in the effective electron temperature up to several thousand Kelvin, as deduced directly from the Drude weight associated with the plasmonic resonances. © 2014 American Chemical Society.
Source Title: Nano Letters
ISSN: 15306984
DOI: 10.1021/nl4042577
Appears in Collections:Staff Publications

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