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|Title:||Ultrafast and nanoscale plasmonic phenomena in exfoliated graphene revealed by infrared pump-probe nanoscopy||Authors:||Wagner, M.
Castro Neto, A.H.
|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. https://doi.org/10.1021/nl4042577||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||URI:||http://scholarbank.nus.edu.sg/handle/10635/98497||ISSN:||15306984||DOI:||10.1021/nl4042577|
|Appears in Collections:||Staff Publications|
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