Suchergebnisse

The unprecedented advance experienced by nano- fabrication techniques and plasmonics research over the past few years has made possible the realization of nanophotonic systems entering into the so-called strong coupling regime between localized surface plasmon (LSP) modes and quantum emitters. Unfortunately, from a theoretical point of view, the field is hindered by the lack of analytical descriptions of the electro- magnetic interaction between strongly hybridized LSP modes and nanoemitters even within the Markovian approximation. This gap is tackled here by exploiting a conformal transformation where a bow-tie nanoantenna excited by a dipole is mapped into a periodic slab−dipole framework whose analytical solution is available. Solving the problem in the transformed space not only provides a straightforward analytical explanation for the original problem (validated using full-wave simulations) but also grants a deep physical insight and simple design guidelines to maximize the coupling between localized dipoles and the bow-tie LSP modes. The results presented here therefore pave the way for a full analytical description of realistic scenarios where quantum dots or dye molecules (modeled beyond a two-level system) are placed near a metallic bow-tie nanoantenna. ; This work was supported in part by the Spanish Government under contract TEC2014-51902-C2-2-R. V.P.-P. is sponsored by Spanish Ministerio de Educación, Cultura y Deporte under grant FPU AP-2012-3796. M.B. is sponsored by the Spanish Government via RYC-2011-08221. A.I.F.-D. acknowledges funding from EU Seventh Framework Programme under grant agreement FP7-PEOPLE-2013-CIG63099. Y.L. would like to acknowledge the funding support from Singapore Ministry of Education (MOE) under grant no. MOE2015-T2-1-145, and NTU-A*STAR Silicon Technologies Centre of Excellence under the program grant no. 11235150003. M.N.-C. was supported by an Imperial College Junior Research Fellowship and is now supported by a Birmingham Fellowship.

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Photonics, copyright © 2018 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acsphotonics.8b00328 ; Very recently it has been predicted that the far-field radiative heat transfer between two macroscopic systems can largely overcome the limit set by Planck's law if one of their dimensions becomes much smaller than the thermal wavelength (λTh≈ 10 μm at room temperature). To explore the ultimate limit of the far-field violation of Planck's law, here we present a theoretical study of the radiative heat transfer between two-dimensional (2D) materials. We show that the far-field thermal radiation exchanged by two coplanar systems with a one-atom-thick geometrical cross section can be more than 7 orders of magnitude larger than the theoretical limit set by Planck's law for blackbodies and can be comparable to the heat transfer of two parallel sheets at the same distance. In particular, we illustrate this phenomenon with different materials such as graphene, where the radiation can also be tuned by a external gate, and single-layer black phosphorus. In both cases the far-field radiative heat transfer is dominated by TE-polarized guiding modes, and surface plasmons play no role. Our predictions provide a new insight into the thermal radiation exchange mechanisms between 2D materials ; This work has been financially supported by the Spanish MINECO (FIS2015-64951-R, MAT2014-53432-C5-5-R, and FIS2017-84057-P), the Comunidad de Madrid (S2013/MIT-2740), the European Union Seventh Framework Programme (FP7-PEOPLE-2013-CIG-630996), and the European Research Council (ERC-2011-AdG-290981 and ERC-2016-STG-714870). V.F.-H. acknowledges support from "la Caixa" Foundation. V.F.-H. and J.C.C. (Mercator Fellow) thank the DFG and SFB767 for sponsoring their stay at the University of Konstanz.

Atomically-sharp tips in close proximity of metal surfaces create plasmonic nanocavities supporting both radiative (bright) and non-radiative (dark) localized surface plasmon modes. Disentangling their respective contributions to the total density of optical states remains a challenge. Electroluminescence due to tunnelling through the tip-substrate gap could allow the identification of the radiative component, but this information is inherently convoluted with that of the electronic structure of the system. In this work, we present a fully experimental procedure to eliminate the electronic-structure factors from the scanning tunnelling microscope luminescence spectra by confronting them with spectroscopic information extracted from elastic current measurements. Comparison against electromagnetic calculations demonstrates that this procedure allows the characterization of the meV shifts experienced by the nanocavity plasmonic modes under atomic-scale gap size changes. Therefore, the method gives access to the frequency-dependent radiative Purcell enhancement that a microscopic light emitter would undergo when placed at such nanocavity ; We acknowledge financial support from the Spanish Ministry for Economy and Competitiveness (grants FIS2015-72482-EXP, FIS2015-64951-R, FIS2016-78591-C3-1-R, PGC2018-098613—B-C21, PGC2018-096047-B-I00, RTI2018-099737-B-I00 and MAT2014-53432-C5-5-R), the regional government of Comunidad de Madrid (grant S2018/NMT-4321), Universidad Autónoma de Madrid (UAM/48 and UAM/134) and IMDEA Nanoscience. Both IMDEA Nanoscience and IFIMAC acknowledge support from the Severo Ochoa and Maria de Maeztu Programmes for Centres and Units of Excellence in R&D (MINECO, Grants SEV-2016-0686 and MDM-2014-0377). We also acknowledge support by the QuantERA program of the European Union with funding by the Spanish AEI through project PCI2018-093145