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Discovery Brings New Type of Fast Computers Closer to Reality
September 28, 2009Physicists at UC San Diego have successfully created speedy integrated circuits with particles called "excitons" that operate at commercially cold temperatures, bringing the possibility of a new type of extremely fast computer based on excitons closer to reality.
Their discovery, detailed this week in the advance online issue of the journal Nature Photonics, follows the team's demonstration last summer of an integrated circuit-an assembly of transistors that is the building block for all electronic devices-capable of working at 1.5 degrees Kelvin above absolute zero. That temperature, equivalent to minus 457 degrees Fahrenheit, is not only less than the average temperature of deep space, but achievable only in special research laboratories.
Now the scientists report that they have succeeded in building an integrated circuit that operates at 125 degrees Kelvin, a temperature that while still a chilly minus 234 degrees Fahrenheit, can be easily attained commercially with liquid nitrogen, a substance that costs about as much per liter as gasoline.
"Our goal is to create efficient devices based on excitons that are operational at room temperature and can replace electronic devices where a high interconnection speed is important," said Leonid Butov, a professor of physics at UCSD, who headed the research team. "We're still in an early stage of development. Our team has only recently demonstrated the proof of principle for a transistor based on excitons and research is in progress."
Excitons are pairs of negatively charged electrons and positively charged "holes" that can be created by light in a semiconductor such as gallium arsenide. When the electron and hole recombine, the exciton decays and releases its energy as a flash of light.
The fact that excitons can be converted into light makes excitonic devices faster and more efficient than conventional electronic devices with optical interfaces, which use electrons for computation and must then convert them to light for use in communications devices.
"Our transistors process signals using excitons, which like electrons can be controlled with electrical voltages, but unlike electrons transform into photons at the output of the circuit," Butov said. "This direct coupling of excitons to photons allows us to link computation and communication."
Other members of the team involved in the discovery were physicists Gabriele Grosso, Joe Graves, Aaron Hammack and Alex High at UC San Diego, and materials scientists Micah Hanson and Arthur Gossard at UC Santa Barbara.
Their research was supported by the Army Research Office, the Department of Energy and the National Science Foundation.
University of California, San Diego
"Our goal is to create efficient devices based on excitons that are operational at room temperature and can replace electronic devices where a high interconnection speed is important," said Leonid Butov, a professor of physics at UCSD, who headed the research team. "We're still in an early stage of development. Our team has only recently demonstrated the proof of principle for a transistor based on excitons and research is in progress."
Excitons are pairs of negatively charged electrons and positively charged "holes" that can be created by light in a semiconductor such as gallium arsenide. When the electron and hole recombine, the exciton decays and releases its energy as a flash of light.
The fact that excitons can be converted into light makes excitonic devices faster and more efficient than conventional electronic devices with optical interfaces, which use electrons for computation and must then convert them to light for use in communications devices.
"Our transistors process signals using excitons, which like electrons can be controlled with electrical voltages, but unlike electrons transform into photons at the output of the circuit," Butov said. "This direct coupling of excitons to photons allows us to link computation and communication."
Other members of the team involved in the discovery were physicists Gabriele Grosso, Joe Graves, Aaron Hammack and Alex High at UC San Diego, and materials scientists Micah Hanson and Arthur Gossard at UC Santa Barbara.
Their research was supported by the Army Research Office, the Department of Energy and the National Science Foundation.
University of California, San Diego
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More Excitons Current Events and Excitons News Articles
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Excitons in Low-Dimensional Semiconductors: Theory, Numerical Methods, Applications (Springer Series in Solid-State Sciences) by Stephan Glutsch (Author) Low-dimensional semiconductors have become a vital part of today's semiconductor physics, and excitons in these systems are ideal objects that bring textbook quantum mechanics to life. Furthermore, their theoretical understanding is important for experiments and optoelectronic devices. The author develops the effective-mass theory of excitons in low-dimensional semiconductors and describes numerical methods for calculating the optical absorption including Coulomb interaction, geometry, and external fields. The theory is applied to Fano resonances in low-dimensional semiconductors and the Zener breakdown in superlattices. Comparing theoretical results with experiments, the book is essentially self-contained; it is a hands-on approach with detailed derivations, worked examples,... |
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Theory of Excitons by Robert S. Knox (Author) | |
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Photosynthetic Excitons by Herbert Van Amerongen (Author), Leonas Valkunas (Author), Rienk Van Grondelle (Author) Contents include structural organization, spectral properties and excitation energy transfer in photosynthesis, the exciton concept, spectral shapes, spectroscopy of excitons in molecular crystals and aggregates, exciton dynamics, nonlinear annihilation of excitons, and more. |
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Excitons: Their Properties and Uses by Donald C. Reynolds (Author) | |
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Self-Trapped Excitons (Springer Series in Solid-State Sciences) by K. S. Song (Author), R. T. Williams (Author) Self-Trapped Excitons discusses the structure and evolution of the self-trapped exciton (STE) in a wide range of materials. It includes a comprehensive review of experiments and extensive tables of data. Emphasis is given throughout to the unity of the basic physics underlying various manifestations of self-trapping, with the theory being developed from a localized, atomistic perspective. The topics treated in detail in relation to STE relaxation include spontaneous symmetry breaking, lattice defect formation, radiation damage, and electronic sputtering. |
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Bose-Einstein Condensation of Excitons and Biexcitons: And Coherent Nonlinear Optics with Excitons by S. A. Moskalenko (Author), D. W. Snoke (Author) Bose-Einstein condensation of excitons is a unique effect in which the electronic states of a solid can self-organize to acquire quantum phase coherence. The phenomenon is closely linked to Bose-Einstein condensation in other systems such as liquid helium and laser-cooled atomic gases. Covering theoretical aspects as well as recent experimental work, the book provides a comprehensive survey of the field. After introducing the relevant basic physics of excitons, the authors discuss exciton-phonon interactions as well as the behavior of biexcitons. They also cover exciton phase-transitions and give particular attention to nonlinear optical effects including the optical Stark effect and chaos in excitonic systems. The thermodynamics of equilibrium, quasiequilibrium, and nonequilibrium... |
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Excitons in molecular crystals;: Theory and applications (Frontiers in chemistry) by David Parker Craig (Author) | |
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Excitons at high density (Springer tracts in modern physics) by H Haken (Author) | |
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Exciton: Webster's Timeline History, 1957 - 2007 by Icon Group International (Author) Webster's bibliographic and event-based timelines are comprehensive in scope, covering virtually all topics, geographic locations and people. They do so from a linguistic point of view, and in the case of this book, the focus is on "Exciton," including when used in literature (e.g. all authors that might have Exciton in their name). As such, this book represents the largest compilation of timeline events associated with Exciton when it is used in proper noun form. Webster's timelines cover bibliographic citations, patented inventions, as well as non-conventional and alternative meanings which capture ambiguities in usage. These furthermore cover all parts of speech (possessive, institutional usage, geographic usage) and contexts, including pop culture, the arts, social sciences... |
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Optics of Excitons in Confined Systems, Proceedings of the INT Meeting, Italy, 24-27 September 1991 (Institute of Physics Conference Series) by D'Andrea (Author) Optics of Excitons in Confined Systems provides an overview of research in semiconductors that exhibit resonance enhanced optical nonlinearities in the frequency range close to the valence-conduction band gap. The book is divided into the following sections: quantum wells, wires, and dots; superlattices; nonlinear optical properties of confined systems; and effects of external fields on confined systems. Topics range from fundamental theory to more applied aspects of excitons in confined sytems. |
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