The Experts below are selected from a list of 4935 Experts worldwide ranked by ideXlab platform

Erwann Bocquillon - One of the best experts on this subject based on the ideXlab platform.

  • A Corner Reflector of graphene Dirac fermions as a phonon-scattering sensor
    Nature Communications, 2019
    Co-Authors: H. Graef, Q. Wilmart, M. Rosticher, D. Mele, L. Banszerus, C. Stampfer, T. Taniguchi, K. Watanabe, J.m. Berroir, Erwann Bocquillon
    Abstract:

    Dirac fermion optics exploits the refraction of chiral fermions across optics-inspired Klein-tunneling barriers defined by high-transparency p-n junctions. We consider the Corner Reflector (CR) geometry introduced in optics or radars. We fabricate Dirac fermion CRs using bottom-gate-defined barriers in hBN-encapsulated graphene. By suppressing transmission upon multiple internal reflections, CRs are sensitive to minute phonon scattering rates. Here we report on doping-independent CR transmission in quantitative agreement with a simple scattering model including thermal phonon scattering. As a signature of CRs, we observe Fabry-Pérot oscillations at low temperature, consistent with single-path reflections. Finally, we demonstrate high-frequency operation which promotes CRs as fast phonon detectors. Our work establishes the relevance of Dirac fermion optics in graphene and opens a route for its implementation in topological Dirac matter.

  • a Corner Reflector of graphene dirac fermions as a phonon scattering sensor
    Nature Communications, 2019
    Co-Authors: H. Graef, Q. Wilmart, M. Rosticher, D. Mele, L. Banszerus, C. Stampfer, T. Taniguchi, K. Watanabe, J.m. Berroir, Erwann Bocquillon
    Abstract:

    Dirac fermion optics exploits the refraction of chiral fermions across optics-inspired Klein-tunneling barriers defined by high-transparency p-n junctions. We consider the Corner Reflector (CR) geometry introduced in optics or radars. We fabricate Dirac fermion CRs using bottom-gate-defined barriers in hBN-encapsulated graphene. By suppressing transmission upon multiple internal reflections, CRs are sensitive to minute phonon scattering rates. Here we report on doping-independent CR transmission in quantitative agreement with a simple scattering model including thermal phonon scattering. As a signature of CRs, we observe Fabry-Perot oscillations at low temperature, consistent with single-path reflections. Finally, we demonstrate high-frequency operation which promotes CRs as fast phonon detectors. Our work establishes the relevance of Dirac fermion optics in graphene and opens a route for its implementation in topological Dirac matter.

H. Graef - One of the best experts on this subject based on the ideXlab platform.

  • A Corner Reflector of graphene Dirac fermions as a phonon-scattering sensor
    Nature Communications, 2019
    Co-Authors: H. Graef, Q. Wilmart, M. Rosticher, D. Mele, L. Banszerus, C. Stampfer, T. Taniguchi, K. Watanabe, J.m. Berroir, Erwann Bocquillon
    Abstract:

    Dirac fermion optics exploits the refraction of chiral fermions across optics-inspired Klein-tunneling barriers defined by high-transparency p-n junctions. We consider the Corner Reflector (CR) geometry introduced in optics or radars. We fabricate Dirac fermion CRs using bottom-gate-defined barriers in hBN-encapsulated graphene. By suppressing transmission upon multiple internal reflections, CRs are sensitive to minute phonon scattering rates. Here we report on doping-independent CR transmission in quantitative agreement with a simple scattering model including thermal phonon scattering. As a signature of CRs, we observe Fabry-Pérot oscillations at low temperature, consistent with single-path reflections. Finally, we demonstrate high-frequency operation which promotes CRs as fast phonon detectors. Our work establishes the relevance of Dirac fermion optics in graphene and opens a route for its implementation in topological Dirac matter.

  • a Corner Reflector of graphene dirac fermions as a phonon scattering sensor
    Nature Communications, 2019
    Co-Authors: H. Graef, Q. Wilmart, M. Rosticher, D. Mele, L. Banszerus, C. Stampfer, T. Taniguchi, K. Watanabe, J.m. Berroir, Erwann Bocquillon
    Abstract:

    Dirac fermion optics exploits the refraction of chiral fermions across optics-inspired Klein-tunneling barriers defined by high-transparency p-n junctions. We consider the Corner Reflector (CR) geometry introduced in optics or radars. We fabricate Dirac fermion CRs using bottom-gate-defined barriers in hBN-encapsulated graphene. By suppressing transmission upon multiple internal reflections, CRs are sensitive to minute phonon scattering rates. Here we report on doping-independent CR transmission in quantitative agreement with a simple scattering model including thermal phonon scattering. As a signature of CRs, we observe Fabry-Perot oscillations at low temperature, consistent with single-path reflections. Finally, we demonstrate high-frequency operation which promotes CRs as fast phonon detectors. Our work establishes the relevance of Dirac fermion optics in graphene and opens a route for its implementation in topological Dirac matter.

J Romeu - One of the best experts on this subject based on the ideXlab platform.

  • transpolarizing trihedral Corner Reflector characterization using a gb sar system
    IEEE Geoscience and Remote Sensing Letters, 2011
    Co-Authors: P J Ferrer, Carlos Lopezmartinez, A Aguasca, Luca Pipia, J M Gonzalezarbesu, X Fabregas, J Romeu
    Abstract:

    The use of a low-profile, lightweight, and easy-to-fabricate transpolarizing surface placed on one side of a trihedral Corner Reflector (TCR) as a polarimetric calibrator is presented in this letter. The transpolarizing TCR presents a high backscattered cross-polar response contrary to standard TCRs. The performance of this device has been tested at the X-band using the Universitat Politecnica de Catalunya ground-based synthetic aperture radar.

Jukka Sarvas - One of the best experts on this subject based on the ideXlab platform.

  • method of moments analysis of the backscattering properties of a corrugated trihedral Corner Reflector
    IEEE Transactions on Antennas and Propagation, 2006
    Co-Authors: Ilari Hanninen, M Pitkonen, K I Nikoskinen, Jukka Sarvas
    Abstract:

    A method of moments (MoM) formulation is developed to analyze the backscattering properties of an anisotropic trihedral Corner Reflector, which is obtained by corrugating one or several of its interior faces. The proposed formulation treats the corrugated surface as ideally tuned to the incident wave frequency. The numerical analysis of the studied structures has been done using closed-form formulas and accurate numerical integration. The focus of the study reported in this paper has been the polarization responses of ideally tuned corrugated Reflectors, which have interesting properties, particularly regarding elliptically or circularly polarized waves. We numerically verify that an appropriately corrugated Reflector returns elliptically and circularly polarized waves with the same handedness as the incident wave. For a linearly polarized incident wave, the Corner Reflector is able to rotate them by 90/spl deg/. Also the effect of the direction of the corrugation to the backscattering properties is studied.

Leo P Ligthart - One of the best experts on this subject based on the ideXlab platform.

  • calibration of a polarimetric radar using a rotatable dihedral Corner Reflector
    IEEE Transactions on Geoscience and Remote Sensing, 1994
    Co-Authors: C M H Unal, R J Niemeijer, J S Van Sinttruyen, Leo P Ligthart
    Abstract:

    Based on the existing mathematical formalisms of radar polarimetry, it is necessary to perform accurate and diversified polarimetric measurements in the real world to thoroughly investigate signature definition, identification, and classification of radar targets. For this study the Delft Atmospheric Research Radar (DARR) is used. This ground-based polarimetric FM-CW radar operates in the S-band. The purpose of the present paper is the polarimetric calibration of the DARR. Among the passive Reflectors, a rotatable dihedral Corner Reflector is a suitable calibration object. It enables one to measure different scattering matrices with only one Reflector. One alignment must be performed and the scattering matrices are measured at the same range. By measuring several scattering matrices, the accuracy of the calibration result can be estimated. A measurement campaign with a rotatable dihedral Corner Reflector was therefore performed. The experimental results and the calibration procedure are presented in this paper. >