Abstract-Collective non-perturbative coupling of 2D electrons with high-quality-factor terahertz cavity photons

• Qi Zhang,
• Minhan Lou,
• Xinwei Li,
• John L. Reno,
• Wei Pan,
• John D. Watson,
• Michael J. Manfra
• & Junichiro Kono

http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3850.html

The collective interaction of electrons with light in a high-quality-factor cavity is expected to reveal new quantum phenomena and find applications in quantum-enabled technologies. However, combining a long electronic coherence time, a large dipole moment, and a high quality-factor has proved difficult. Here, we achieved these conditions simultaneously in a two-dimensional electron gas in a high-quality-factor terahertz cavity in a magnetic field. The vacuum Rabi splitting of cyclotron resonance exhibited a square-root dependence on the electron density, evidencing collective interaction. This splitting extended even where the detuning is larger than the resonance frequency. Furthermore, we observed a peak shift due to the normally negligible diamagnetic term in the Hamiltonian. Finally, the high-quality-factor cavity suppressed superradiant cyclotron resonance decay, revealing a narrow intrinsic linewidth of 5.6 GHz. High-quality-factor terahertz cavities will enable new experiments bridging the traditional disciplines of condensed-matter physics and cavity-based quantum optics.

Abstract-Tunable surface plasmon instability leading to emission of radiation

Godfrey Gumbs^1,2, Andrii Iurov^1,3,a), Danhong Huang⁴ and Wei Pan⁵
http://scitation.aip.org/content/aip/journal/jap/118/5/10.1063/1.4927101
1 Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10065, USA
2 Donostia International Physics Center (DIPC), P de Manuel Lardizabal, 4, 20018 San Sebastian, Basque Country, Spain
3 Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico 87106, USA
4 Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, New Mexico 87117, USA
5 Sandia National Laboratory, Albuquerque, New Mexico 87185, USA
a) Electronic mail: aiurov@chtm.unm.edu
J. Appl. Phys. 118, 054303 (2015); http://dx.doi.org/10.1063/1.4927101

We propose a new approach for energy conversion from a dc electric field to tunable terahertz emission based on hybrid semiconductors by combining two-dimensional (2D) crystalline layers and a thick conducting material with possible applications for chemical analysis, security scanning, medical (single-molecule) imaging, and telecommunications. The hybrid nano-structure may consist of a single or pair of sheets of graphene, silicene, or a 2D electron gas.When an electric current is passed through a 2D layer, we discover that two low-energy plasmon branches exhibit a characteristic loop in their dispersion before they merge into an unstable region beyond a critical wave vector qc . This finite qc gives rise to a wavenumber cutoff in the emission dispersion of the surface plasmon induced instability and emission of radiation(spiler). However, there is no instability for a single driven layer far from the conductor, and theinstability of an isolated pair of 2D layers occurs without a wavenumber cutoff. The wavenumber cutoff is found to depend on the conductor electron density, layer separation, distances of layers from the conductor surface, and the driving-current strength.

Abstract-Superradiant Decay of Cyclotron Resonance of Two-Dimensional Electron Gases

Qi Zhang, Takashi Arikawa, Eiji Kato, John L. Reno, Wei Pan, John D. Watson, Michael J. Manfra, Michael A. Zudov, Mikhail Tokman, Maria Erukhimova, Alexey Belyanin, and Junichiro Kono
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.113.047601

We report on the observation of collective radiative decay, or superradiance, of cyclotron resonance (CR) in high-mobility two-dimensional electron gases in GaAs quantum wells using time-domain terahertz magnetospectroscopy. The decay rate of coherent CR oscillations increases linearly with the electron density in a wide range, which is a hallmark of superradiant damping. Our fully quantum mechanical theory provides a universal formula for the decay rate, which reproduces our experimental data without any adjustable parameter. These results firmly establish the many-body nature of CR decoherence in this system, despite the fact that the CR frequency is immune to electron-electron interactions due to Kohn’s theorem.

DOI: http://dx.doi.org/10.1103/PhysRevLett.113.047601

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• Published 21 July 2014
• Received 5 May 2014

© 2014 American Physical Society

Abstract-Probing terahertz surface plasmon waves in graphene structures

Oleg Mitrofanov^1,2, Wenlong Yu³, Robert J. Thompson¹, Yuxuan Jiang³, Igal Brener^2,4, Wei Pan⁴, Claire Berger^3,5, Walter A. de Heer³, and Zhigang Jiang³

¹Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom
²Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
³School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
⁴Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
⁵CNRS/Institut Néel, BP166, 38042 Grenoble, France

Epitaxial graphene mesas and ribbons are investigated using terahertz (THz) near-field microscopy to probe surface plasmon excitation and THz transmission properties on the sub-wavelength scale. The THz near-field images show variation of graphene properties on a scale smaller than the wavelength, and excitation of THz surface waves occurring at graphene edges, similar to that observed at metallic edges. The Fresnel reflection at the substrate SiC/air interface is also found to be altered by the presence of graphene ribbon arrays, leading to either reduced or enhanced transmission of the THz wave depending on the wave polarization and the ribbon width.

© 2013 Author(s).All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License