Download or read book Optically detected resonances induced by far infrared radiation in quantum wells and quantum dots written by Michael Gerbracht and published by GRIN Verlag. This book was released on 2008-07-18 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: Doctoral Thesis / Dissertation from the year 2008 in the subject Physics - Theoretical Physics, grade: 1,0, University of Dortmund (Experimentelle Physik II), language: English, abstract: Abstract Photoluminescence (PL) and optically detected resonances (ODR) where studied on semiconductor quantum wells and quantum dots. Magnetic fields of up to 33 T where applied to samples at temperatures between 0.25 K and 10 K. In nonmagnetic quantum wells optically detected cyclotron resonance was used to determine basic properties such as effective mass and mobility of GaAs/AlGaAs quantum wells. In CdTe/CdMgTe quantum wells evidence for the singlet and triplet state of the negatively and positively charged exciton was found at high magnetic fields. In a highly n-type doped GaAs/AlGaAs quantum well, signatures of the fractional quantum hall effect were observed in PL and ODR data. Also shake up processes in a variety of quantum wells are discussed. In magnetic quantum wells, cusps in the exciton shift are present at moderate magnetic fields which could be assigned to next nearest neighbor interactions between Mn2+ ion pairs and single ions. Resonances in InGaAs/GaAs quantum dots induced by far-infrared radiation have been observed optically. They were studied in quantum dots with different confinement potential and under a series of tilting angles between sample normal and magnetic field direction. The resonances could be assigned to trion formation due to cyclotron resonance in the wetting layer and transitions in the internal energy structure of the dots. Also magnetic CdMnTe/ZnCdTe quantum dots with different Mn content were measured at magnetic fields up to 17 T. At low Mn concentrations a competition between the giant and intrinsic Zeeman splitting leads to a reduction of the polarization of the sample at high magnetic field which makes it possible to determine the Mn content by photoluminescence measurements.
Download or read book Terahertz Spectroscopy written by Susan L. Dexheimer and published by CRC Press. This book was released on 2017-12-19 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of new sources and methods in the terahertz spectral range has generated intense interest in terahertz spectroscopy and its application in an array of fields. Presenting state-of-the-art terahertz spectroscopic techniques, Terahertz Spectroscopy: Principles and Applications focuses on time-domain methods based on femtosecond laser sources and important recent applications in physics, materials science, chemistry, and biomedicine. The first section of the book examines instrumentation and methods for terahertz spectroscopy. It provides a comprehensive treatment of time-domain terahertz spectroscopic measurements, including methods for the generation and detection of terahertz radiation, methods for determining optical constants from time-domain measurements, and the use of femtosecond time-resolved techniques. The last two sections explore a variety of applications of terahertz spectroscopy in physics, materials science, chemistry, and biomedicine. With chapters contributed by leading experts in academia, industry, and research, this volume thoroughly discusses methods and applications, setting it apart from other recent books in this emerging terahertz field.
Download or read book Intersubband Transitions in Quantum Wells Physics and Devices written by Sheng S. Li and published by Springer Science & Business Media. This book was released on 2013-11-27 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: The International Workshop on "Intersubband Transitions in Quantum Wells:: Physics and Applications," was held at National Cheng Kung University, in Tainan, Taiwan, December 15-18, 1997. The objective of the Workshop is to facilitate the presentation and discussion of the recent results in theoretical, experimental, and applied aspects of intersubband transitions in quantum wells and dots. The program followed the tradition initiated at the 1991 conference in Cargese-France, the 1993 conference in Whistler, B. C. Canada, and the 1995 conference in Kibbutz Ginosar, Israel. Intersubband transitions in quantum wells and quantum dots have attracted considerable attention in recent years, mainly due to the promise of various applications in the mid- and far-infrared regions (2-30 J. lm). Over 40 invited and contributed papers were presented in this four-day workshop, with topics covered most aspects of the intersubband transition phenomena including: the basic intersubband transition processes, multiquantum well infrared photodetector (QWIP) physics, large format (640x480) GaAs QWIP (with 9. 0 J. lffi cutoff) focal plane arrays (FPAs) for IR imaging camera applications, infrared modulation, intersubband emission including mid- and long- wavelength quantum cascade (QC) lasers such as short (A. "" 3. 4 J. lm) and long (A. "" 11. 5 J. lm) wavelength room temperature QC lasers, quantum fountain intersubband laser at 15. 5 J. lm wavelength in GaAs/AIGaAs quantum well, harmonic generation and nonlinear effects, ultra-fast phenomena such as terahertz (THz) intersubband emission and detection. The book divides into five Chapters.
Download or read book Intersubband Transitions in Quantum Wells Physics and Devices written by Sheng S. Li and published by Springer. This book was released on 1998-07-31 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of Intersubband Transitions in Quantum Wells: Physics and Devices is to facilitate the presentation and discussion of the recent results in theoretical, experimental, and applied aspects of intersubband transitions in quantum wells and dots. This reference work is based on the International Workshop that was held at National Cheng Kung University in Tainan, Taiwan in December 15-18, 1997. Intersubband transitions in quantum wells and quantum dots have attracted considerable attention in recent years, mainly due to the promise of various applications in the mid- and far-infrared regions (2-30 mum). Over 40 invited and contributed papers were presented in this four-day workshop, with topics covering most aspects of the intersubband transition phenomena including: the basic intersubband transition process, multiquantum well infrared photodetector (QWIP) physics, large format (640×480) GaAs QWIP (with 9.0 mum cutoff) focal plane arrays (FPAs) for IR imaging camera applications, infrared modulation, intersubband emission including mid- and long-wavelength quantum cascade (QC) lasers such as short (lambda = 3.4 mum) and long (lambda = 11.5 mum) wavelength room temperature QC lasers, quantum fountain intersubband laser at 15.5 mum wavelength in GaAs/AIGaAs quantum well, harmonic generation and nonlinear effects, ultra-fast phenomena such as terahertz (THz) intersubband emission and detection. Intersubband Transitions in Quantum Wells: Physics and Devices will be of interest to researchers from universities and industrial laboratories working on physics and devices of nanostructures, and researchers in the infrared (IR) community.
Download or read book Far Infrared Magneto optical Studies of Spin Effects and Off Diagonal Conductivity in the Integer Quantum Hall Regime written by Andreas Volker Stier and published by . This book was released on 2011 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: The motivation for this dissertation is the study of the integer quantum Hall effect. Two different topics are explored based on the complementary theoretical view of this effect. On the one hand, topologically protected edge states contribute to the current distribution in samples containing a two dimensional electron gas in a high magnetic field. These edge channels are robust against scattering and can be viewed as one- dimensional conductors along the edges of the sample where dissipationless transport occurs. We have studied the effect of spin-orbit interaction on those edge channels. These experiments are important both from a technological point of view as well as from a fundamental scientific perspective. The former is motivated by the emerging field of spintronics and quantum computation. Within that framework, the utilization of the electrons spin is regarded as a superior method to process information and to conduct computations.^The latter point is that to our knowledge the effect of spin- orbit interaction on the width and formation of edge channels has so far only theoretically been addressed. We have utilized a sensitive photoconductivity approach to study electric-dipole induced spin resonances (EDSR) between spin-split incompressible quantum Hall edge channels. Linearly polarized monochromatic far infrared radiation from a molecular gas laser induced changes in the longitudinal resistance of a two dimensional electron gas (2DEG) in an asymmetric InAs quantum well in the quantum Hall regime; the photo response (PR). We observe non resonant bolometric PR from the heating of the 2DEG, resonant bolometric PR from cyclotron resonant absorption and sharp pairs of resonance features in the vicinity of the odd filling factor n=7, which we associate with EDSR transitions between pairs of incompressible quantum Hall edge channels.^We study the behavior of the resonances as a function of angle between the sample normal and magnetic field and find an unexpected splitting of the resonance features with angle; the resonance feature which we associate with the EDSR transition from the topmost Landau level abruptly disappears below a critical angle. A study of the resonances with changed applied current reveals another unexpected behavior as that the central resonance feature splits in applied magnetic field with increased applied current. We introduce a detailed model based on the vector addition of applied and effective spin- orbit magnetic field that yields a total magnetic field which couples to the spin of the electrons in the incompressible quantum Hall edge channels. This model qualitatively reproduces all the experimentally observed effects and semi-quantitatively reproduces the splitting of two pairs of resonance features with angle.^We discuss the splitting of the central resonance pair with increased current and find a mechanism explaining the possibility of the observed effect. The second part of this dissertation is based on the quantum Hall picture of localization. The electronic wavefunction in a two dimensional electron gas are bound to scattering centers, which leads to a theoretical description of the Landau level density of states that is comprised of localized and delocalized states. States are localized and therefore do not contribute to longitudinal current flow when the extent of the wavefunction is smaller than the sample size. Within a recent theory of dynamical scaling, the effective sample size is reduced in the ac regime with increasing frequency. At high frequency, the quantum Hall plateau is predicted to vanish due to the delocalization of all electronic states. We have studied a 2DEG in a GaAs/AlGaAs heterostructure close to cyclotron resonance utilizing a polarization modulation method.^We measure the Faraday rotation close to cyclotron resonance as a function of frequency, temperature and 2DEG density and find for the first time features in the Faraday rotation associated with the dc integer quantum Hall effect. We analyze the features with a scaling theory and find scaling behavior favoring long range electron-electron interactions as the dominant mechanism for localization.
Download or read book Parabolically Graded Semiconductor Quantum Wells for Emission of Far infrared Radiation written by Kevin D. Maranowski and published by . This book was released on 2000 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Manipulating Quantum Coherence in Solid State Systems written by Michael E. Flatté and published by Springer Science & Business Media. This book was released on 2007-05-30 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book features the proceedings of the NATO Advanced Study Institute "Manipulating Quantum Coherence in Solid State Systems", held in Cluj-Napoca, Romania, August 2005, which presented a fundamental introduction to solid-state approaches to achieving quantum computation. This proceedings volume describes the properties of quantum coherence in semiconductor spin-based systems and the behavior of quantum coherence in superconducting systems.
Download or read book Quantum Coherence Correlation and Control in Finite Quantum Systems written by Hui Yan and published by Frontiers Media SA. This book was released on 2022-10-21 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2008 with total page 902 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics Briefs written by and published by . This book was released on 1994 with total page 1256 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Acta Physica Polonica written by and published by . This book was released on 2004 with total page 924 pages. Available in PDF, EPUB and Kindle. Book excerpt: General physics, solid state physics, applied physics.
Download or read book Electrical Electronics Abstracts written by and published by . This book was released on 1997 with total page 2240 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book JJAP written by and published by . This book was released on 1999 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 692 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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Download or read book JJAP Letters written by and published by . This book was released on 1998 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ceramic Abstracts written by and published by . This book was released on 1999 with total page 950 pages. Available in PDF, EPUB and Kindle. Book excerpt:
