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Unlocking the secret of the Kondo Effect
September 22, 2008A team of scientists including researchers from the London Centre for Nanotechnology at UCL (University College London) and the IBM Almaden Research Center has forged a breakthrough in understanding an intriguing phenomenon in fundamental physics: the Kondo effect. The findings are reported online today in the scientific journal Nature Physics.
The Kondo effect, one of the few examples in physics where many particles collectively behave as one object (a single quantum-mechanical body), has intrigued scientists around the world for decades. When a single magnetic atom is located inside a metal, the free electrons of the metal 'screen' the atom. That way, a cloud of many electrons around the atom becomes magnetized. Sometimes, if the metal is cooled down to very low temperatures, the atomic spin enters a so-called 'quantum superposition' state. In this state its north-pole points in two opposite directions at the same time. As a result, the entire electron cloud around the spin will also be simultaneously magnetized in two directions.
Now, using a technique that was developed by the same team in 2007, the researchers have shown that it is possible to predict when the Kondo effect will occur - and to understand why. The key turns out to be in the geometry of a magnetic atom's immediate surroundings. By carefully studying how this geometry influences the magnetic moment (or "spin") of the atom, the emergence of the Kondo effect can now be predicted and understood.
Dr. Cyrus Hirjibehedin, a member of the IBM team who is now a Lecturer at UCL (University College London) and a part of the academic staff of the LCN, said: "This result represents a major advance in our understanding of this fundamental physical phenomenon and could have important consequences for future nanoscale magnetic devices."
University College London
Dr. Cyrus Hirjibehedin, a member of the IBM team who is now a Lecturer at UCL (University College London) and a part of the academic staff of the LCN, said: "This result represents a major advance in our understanding of this fundamental physical phenomenon and could have important consequences for future nanoscale magnetic devices."
University College London
Nanophysicists find unexpected magnetic effect
Spanish and U.S. physicists studying nanoelectronics have found that size really does matter when it comes to predicting the behavior of electrical contacts that are just one atom wide.
Physicists tailor magnetic pairings in nanoscale semiconductors
Electrons love to zip around metals such as copper, especially if the metal is cooled to temperatures near absolute zero. But if they encounter a magnetic atom (say, iron) during their travels, the electrons will try to "screen," or cancel out, the magnetic atom's spin alignment by pairing with it. This pairing modifies the flow of electrons in the metal, in a phenomenon called the Kondo effect.
Delicate Relation between Single Spins
Probing the magnetic interaction between single atoms is no longer a dream. Using a scanning tunnelling microscope, the interaction of the spins of two neighbouring cobalt atoms adsorbed at a copper surface has been measured as a function of their distance with atomic precision.
More Kondo Effect Current Events and Kondo Effect News Articles
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Exotic Kondo Effects in Metals: Magnetic Ions in a Crystalline Electric Field and Tunnelling Centres by D L Cox (Author), A Zawadowski (Author) This provides a major review of the two-level system Kondo model, as applied to metallic glasses, nanoscale devices and some doped semiconductors; and the quadripolar and magnetic two-channel Kondo models developed for rare-earth and actinide ions with crystal splitting metals. These contrast with the simple single-channel model, and allow the study of non-Fermi liquid physics. This book forms a valuable and unique source of information for statistical and condensed matter physicists and graduate students. Key Features: * An invaluable and unique source of information on this highly popular area of condensed matter physics * Based upon a special edition of the Advances in Physics journal * Magnetic impurities in metals present a major challenge to condensed matter... |
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Kondo Effect and Dephasing in Low-Dimensional Metallic Systems (NATO Science Series II: Mathematics, Physics and Chemistry) by Venkat Chandrasekhar (Editor), Chris Van Haesendonck (Editor), Alfred Zawadowski (Editor) The Kondo effect is relevant to many branches of condensed matter physics, including heavy-fermion physics, correlated electron systems, and high-temperature superconductivity. Nanolithographic fabrication techniques and new spectroscopic measuring tools (scanning tunneling microscopy, mechanically controllable break junctions, etc.) mean we can probe the Kondo effect directly on the relevant mesoscopic size scale. This book brings together the major experimental and theoretical progress that has been made during the past few years on low-dimensional Kondo systems. The following questions are addressed. + The relevance of the Kondo screening cloud, surface-induced anisotropy and disorder to an understanding of the size dependence of the Kondo transport properties in... |
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The Kondo Problem to Heavy Fermions (Cambridge Studies in Magnetism) by Alexander Cyril Hewson (Author) This book deals with the concepts and techniques that have been developed to meet this challenge and with their application to the interpretation of experiment. The author surveys in detail the many-body techniques, scaling, renormalization group, Fermi liquid and Bethe ansatz, which lead to a solution of the Kondo problem for most of the theoretical models. The book also deals with special techniques for N-fold degenerate models for rare earth magnetic impurities. The many-body techniques developed to deal with strong correlation impurity problems have also been extended to provide a partial explanation of heavy fermion behavior. |
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Extended Le Chatelier's formula for carbon dioxide dilution effect on flammability limits [An article from: Journal of Hazardous Materials] by S. Kondo (Author), K. Takizawa (Author), A. Takahashi (Author), K. Tokuhashi (Author) This digital document is a journal article from Journal of Hazardous Materials, published by Elsevier in 2006. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser. Description: Carbon dioxide dilution effect on the flammability limits was measured for various flammable gases. The obtained values were analyzed using the extended Le Chatelier's formula developed in a previous study. As a result, it has been found that the flammability limits of methane, propane, propylene, methyl formate, and 1,1-difluoroethane are adequately explained by the extended Le Chatelier's formula using a common set of parameter values. Ethylene, dimethyl ether, and ammonia behave differently from... |
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Theory of Magnetism (Springer Series in Solid-State Sciences) by Kei Yosida (Author) Theory of Magnetism is an important subfield of the theory of solids, and has guided a long history of research into the phenomenon of magnetism. This book provides the foundation for further development in this field. Its contents are divided into four parts. In Part I, Magnetic Ions in Crystals, the electron states of magnetic ions in crystals and the exchange interactions between them are explained. Part II, Magnetism of Spin Systems, treats problems of ferromagnetism and antiferromagnetism shown by exchange-coupled localized spin systems. In Part III, Magnetism of Metals, magnetic properties of itinerant electron systems are discussed in relation to 3d electrons in iron-group metals. Part IV, Magnetism of Dilute Alloys, is devoted to an explanation of the Kondo effect and related... |
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Sex-specific effects of gonadal steroids on conspecific odor preference in the rat [An article from: Hormones and Behavior] by K. Xiao (Author), Y. Kondo (Author), Y. Sakuma (Author) This digital document is a journal article from Hormones and Behavior, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser. Description: Effects of gonadal steroids on conspecific odor preference for either (1) sexually active male or active female, (2) sexually active or gonadectomized (gdx) males, (3) sexually active or gdx females, and (4) gdx males or gdx females were determined in male and female rats in a three-chamber apparatus. For the first test, gdx females were made sexually active by treatments with estradiol benzoate (EB) and progesterone (P), and sexually active males were selected by prior screening. Sexually active males and... | |
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Fermi Surface Effects by J Kondo (Author) | |
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Health Effects of Low Level Radiation by Sohei Kondo (Author) | |
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Fermi Surface Effects: Proceedings (Springer Series in Solid-State Sciences) by J. Kondo (Author), A. Yoshimori (Editor) Each of the five review lectures in Fermi Surface Effects concentrates on a particular aspect of the behavior of metal electrons. The topics chosen include quantum tunneling of protons and muons in metals, singularities in the x-ray spectra of metals, properties of magnetic impurities in metals in terms of the Anderson model, Fermi surface effects in scattering of aroms and molecules from metal surfaces, and heavy fermion systems. | |
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Note on the Kondo effect of the superconducting dilute alloy (Technical report of ISSP) by Kiyoshi Kawamura (Author) |
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