Possible new effects in superconductive tunnelling
About: This article is published in Physics Letters.The article was published on 1962-07-01. It has received 3334 citations till now. The article focuses on the topics: Quantum tunnelling.
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TL;DR: The mathematical theory of the method is explained in detail, followed by a thorough description of MEG instrumentation, data analysis, and practical construction of multi-SQUID devices.
Abstract: Magnetoencephalography (MEG) is a noninvasive technique for investigating neuronal activity in the living human brain. The time resolution of the method is better than 1 ms and the spatial discrimination is, under favorable circumstances, 2-3 mm for sources in the cerebral cortex. In MEG studies, the weak 10 fT-1 pT magnetic fields produced by electric currents flowing in neurons are measured with multichannel SQUID (superconducting quantum interference device) gradiometers. The sites in the cerebral cortex that are activated by a stimulus can be found from the detected magnetic-field distribution, provided that appropriate assumptions about the source render the solution of the inverse problem unique. Many interesting properties of the working human brain can be studied, including spontaneous activity and signal processing following external stimuli. For clinical purposes, determination of the locations of epileptic foci is of interest. The authors begin with a general introduction and a short discussion of the neural basis of MEG. The mathematical theory of the method is then explained in detail, followed by a thorough description of MEG instrumentation, data analysis, and practical construction of multi-SQUID devices. Finally, several MEG experiments performed in the authors' laboratory are described, covering studies of evoked responses and of spontaneous activity in both healthy and diseased brains. Many MEG studies by other groups are discussed briefly as well.
4,533 citations
TL;DR: The 2010 self-consistent set of values of the basic constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for international use is presented in this article.
Abstract: This paper gives the 2010 self-consistent set of values of the basic constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for international use. The 2010 adjustment takes into account the data considered in the 2006 adjustment as well as the data that became available from 1 January 2007, after the closing date of that adjustment, until 31 December 2010, the closing date of the new adjustment. Further, it describes in detail the adjustment of the values of the constants, including the selection of the final set of input data based on the results of least-squares analyses. The 2010 set replaces the previously recommended 2006 CODATA set and may also be found on the World Wide Web at physics.nist.gov/constants.
2,770 citations
TL;DR: In this article, the authors discuss the results in the context of related developments, including Andreev reflection, shot noise, conductance quantization and dynamical Coulomb blockade.
1,346 citations
TL;DR: Optical lattices represent a fast-paced modern and interdisciplinary field of research as discussed by the authors, and they form powerful model systems of quantum many-body systems in periodic potentials for probing nonlinear wave dynamics and strongly correlated quantum phases, building fundamental quantum gates or observing Fermi surfaces.
Abstract: Artificial crystals of light, consisting of hundreds of thousands of optical microtraps, are routinely created by interfering optical laser beams. These so-called optical lattices act as versatile potential landscapes to trap ultracold quantum gases of bosons and fermions. They form powerful model systems of quantum many-body systems in periodic potentials for probing nonlinear wave dynamics and strongly correlated quantum phases, building fundamental quantum gates or observing Fermi surfaces in periodic potentials. Optical lattices represent a fast-paced modern and interdisciplinary field of research.
1,298 citations
TL;DR: In this article, the authors provide a theoretical basis for understanding the current phase relation (CPhiR) for the stationary Josephson effect in various types of superconducting junctions.
Abstract: This review provides a theoretical basis for understanding the current-phase relation (CPhiR) for the stationary (dc) Josephson effect in various types of superconducting junctions The authors summarize recent theoretical developments with an emphasis on the fundamental physical mechanisms of the deviations of the CPhiR from the standard sinusoidal form A new experimental tool for measuring the CPhiR is described and its practical applications are discussed The method allows one to measure the electrical currents in Josephson junctions with a small coupling energy as compared to the thermal energy A number of examples illustrate the importance of the CPhiR measurements for both fundamental physics and applications
1,084 citations
Cites background or methods from "Possible new effects in superconduc..."
...Josephson (1962) predicted that a supercurrent IS could exist between two superconductors separated by a thin insulating layer and that its value would be proportional to the sine of the difference w5x12x2 of the phases of the superconductor order parameters D1 exp$ix1% and D2 exp$ix2%, IS~w!...
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...The simplest case of an ideal tunnel junction, with the barrier modeled by a delta functional potential, was originally considered by Josephson (1962)....
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...A supercurrent in a tunnel SIS contact depends linearly on the barrier transparency, since Cooper pairs tunnel coherently (Josephson, 1962)....
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...A. Ideal tunnel junctions Ambegaokar and Baratoff (1963) used the Green’sfunction method to generalize the calculation of Josephson (1962) to finite temperatures....
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References
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TL;DR: A generalization of the method elaborated by the author for the theory of superconductivity is presented in this paper, where the ground state and its fermion excitations are considered.
Abstract: A generalization of the method elaborated by the author for the theory of superconductivity is presented. It is shown that the original Frohlich model possesses the property of superconductivity. The ground state and its fermion excitations are considered.
1,033 citations
TL;DR: In this paper, a generalization of the random-phase approximation of the theory of Coulomb correlation energy is applied to the superconductivity theory, and it is shown that most elementary excitations have the Bardeen-Cooper-Schrieffer energy gap spectrum, but there are collective excitations also.
Abstract: A generalization of the random-phase approximation of the theory of Coulomb correlation energy is applied to the theory of superconductivity. With no further approximations it is shown that most of the elementary excitations have the Bardeen-Cooper-Schrieffer energy gap spectrum, but that there are collective excitations also. The most important of these are the longitudinal waves which have a velocity ${v}_{F}{{\frac{1}{3}[1\ensuremath{-}4N(0)|V|]}}^{\frac{1}{2}}$ in the neutral Fermi gas, and are essentially unperturbed plasma oscillations in the charged case. Other collective excitations resembling higher bound pair states may or may not exist but do not seriously affect the energy gap. The theory obeys the sum rules and is gauge invariant to an adequate degree throughout.
943 citations
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01 Jan 1959TL;DR: In this paper, a criterion for the superfluidity of a Fermi system with a four-line vertex Hamiltonian is established, and the effect on superconductivity of the Coulomb interaction between the electrons is analyzed.
Abstract: The method of canonical transformations proposed by one of the authors ten years ago in connection with a microscopic theory of superfluidity for Bose systems, is generalized here to Fermi systems, and forms the basis of a method for investigating the problem of superconductivity.
Starting from Frohlich's Hamiltonian, the energy of the superconducting ground state and the one-Fermion and collective excitations corresponding to this state are obtained. It turns out that the final formulae for the ground state and one-Fermion excitations recently obtained by Bardeen, Cooper and Schrieffer are correct in the first approximation. The physical picture appears to be closer to the one proposed by Schafroth, Butler and Blatt.
The effect on superconductivity of the Coulomb interaction between the electrons is analyzed in detail. A criterion for the superfluidity of a Fermi system with a four-line vertex Hamiltonian is established.
521 citations