TST, Vol. 2, No. 1, PP. 1-14
Radiation-induced magnetoresistance oscillations in high-mobility two-dimensional semiconductors
X. L. Lei
Department of Physics, Shanghai Jiaotong University,
1954 Huashan Road, Shanghai 200030, China
Abstract: We give a brief overview to a systematic theoretical treatment on radiation induced magnetoresistance oscillations in high-mobility two-dimensional electron systems, based on the balance-equation approach to magnetotransport which is developed for high-carrier-density systems. The model covers regimes of both inter- and intra-Landau level processes, takes full account of multiphoton-assisted electron transitions as well as radiation-induced change of the electron distribution, and naturally includes electrodynamic damping. Electron scatterings by impurities, transverse and longitudinal acoustic phonons as well as polar optic phonons are considered in GaAs-based heterosystems with realistic scattering potentials. This theoretical model reproduces the main features of magnetoresistance oscillations, predicts the appearance of the measured zero resistance, and explains the rapid temperature decay of the oscillatory photoresistance as observed in many prominent experiments.
Keywords: Magnetoresistance oscillation, two-dimensional semiconductor, THz radiation
doi: 10.11906/TST.001-014.2009.03.01
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TST, Vol. 2, No. 1, PP. 15-22
Flexible Quasi-Three-Dimensional Terahertz Electric Metamaterials
Abul K. Azad,1* Hou-Tong Chen,1 Xinchao Lu,2 Jianqiang Gu,2 Nina R.
Weisse-Bernstein,3 Elshan Akhadov,1 Antoinette J. Taylor,1 Weili Zhang,2 and John F.O’Hara1
1MPA-CINT, Los Alamos National Laboratory, P. O. Box 1663, MS K771, Los Alamos,
New Mexico 87545, USA
2School of Electrical and Computer Engineering, Oklahoma State University, Stillwater,
OK 74078, USA
3ISR-2, Space and Remote Sensing, Los Alamos National Laboratory, P. O. Box 1663, MS
B244, Los Alamos, NM 87545, USA
*Email: aazad@lanl.gov
Abstract: We fabricate quasi-three-dimensional terahertz electric metamaterials by stacking multiple single-layer planar metamaterials fabricated on thin, flexible polyimide substrates. Terahertz time-domain spectroscopy is used to characterize their transmission properties, with which we obtain the frequency dependent complex effective dielectric functions. Increasing the number of layers reduces the resonant transmission minimum, while the extracted effective dielectric functions are independent on the number of layers. The results reveal that the real portions of the dielectric functions only show positive values, however, decreasing the thickness of the polyimide substrates, and thereby the spacing between the adjacent split-ring resonator layers, enables negative electric response.
Keywords: Terahertz, Metamaterials, Effective dielectric functions, Quasi-three-dimensional, Polyimide.
doi: 10.11906/TST.015-022.2009.03.02
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TST, Vol. 2, No. 1, PP. 23-30
Electric and Magnetic Responses from Metamaterial Unit Cells at Terahertz
Wen Xuan Tang, Qiang Cheng, and Tie Jun Cui*
State Key Laboratory of Millimeter Waves
Institute of Target Characteristics and Identification
School of Information Science and Engineering, Southeast University
Nanjing, 210096, China
*Email: tjcui@seu.edu.cn
Abstract: Metamaterials are artificial media with novel electromagnetic properties. We study the metamaterial unit cells at terahertz frequencies, investigate their electric and magnetic responses to the incident wave, and retrieve their effective material parameters. Simulation results reveal the origins of the effective permittivity and permeability and prove the predicted responses persuasively. In addition, we prove that symmetric resonant structures exhibit purer resonance properties than the asymmetric ones exhibit purer resonance than the asymmetric ones.
Keywords: Metamaterials, Terahertz, Electric and magnetic responses
doi: 10.11906/TST.023-030.2009.03.03
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TST, Vol. 2, No. 1, PP. 31-38
Spectral Responses by Chains of Subwavelength-Size Metallic Spheres in Terahertz (THz) Region
Wei Yan, Hua Chen, Yimin Sun and Li Wang*
Laboratory of Optical Physics, Institute of Physics and Center for Condensed Matter Physics,
Chinese Academy of Sciences, Beijing 100190, China
*Email: wangli@aphy.iphy.ac.cn
Abstract: The extinction spectra for chains of subwavelength-sized metal spheres responding to incident terahertz plane waves are calculated in 0.1-2.5THz frequency range using a generalized Mie theory. It is found that the coherent coupling between the spheres varies as the number N of spheres in the ensemble increases and finally approaches a steady response, which manifests that the collective excitation of the spheres only exists within a finite spatial scope. Therefore, the spectral responses of the systems strongly depend on the polarization of incident waves, diameter and interspacing of spheres while the detailed conductive properties of metals only play a minor role. Especially, the interaction of the L-mode incident field whose electric field parallel to the array of spheres, with the ensemble, is much stronger than that of the T-mode and shows complicated resonant features.
Key words: terahertz, metamaterials, metallic spheres, extinction spectrum
doi: 10.11906/TST.031-038.2009.03.04
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