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Superconductivity Of Metals And Alloys
P. G. De Gennes
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eBook - ePub
Superconductivity Of Metals And Alloys
P. G. De Gennes
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About This Book
Drawn from the author's introductory course at the University of Orsay, Superconductivity of Metals and Alloys is intended to explain the basic knowledge of superconductivity for both experimentalists and theoreticians. These notes begin with an elementary discussion of magnetic properties of Type I and Type II superconductors. The microscopic theory is then built up in the Bogolubov language of self-consistent fields. This text provides the classic, fundamental basis for any work in the field of superconductivity.
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1
FUNDAMENTAL PROPERTIES
1–1 A NEW CONDENSED STATE
We take a piece of tin and cool it down; at a temperature T0 = 3.7°K we find a specific heat anomaly (Fig. 1-1a). Below T0 the tin is in a new thermodynamical state. What has happened?
It is not a change in the crystallographic structure, as far as x rays can tell. It is not a ferromagnetic, or antiferromagnetic, transition. (It can be seen by magnetic scattering of neutrons, that tin carries no magnetic moment on an atomic scale.) The striking new property is that the tin has zero electrical resistance. (For instance, a current induced in a tin ring has been observed to persist over times > 1 year.) We say that tin, in this particular phase, is a superconductor, and we call the permanent current a supercurrent.
A large number of metals and alloys are superconductors, with critical temperatures T0 ranging from less than 1°K to 18°K. Even some heavily doped semiconductors have been found to be superconductors.
Historically, the first superconductor (mercury) was discovered by Kammerling Onnes in 1911.
The free energy FS in the superconducting phase can be derived from the specific heat data and is represented on Fig. 1-1b (solid line). The dotted line gives the corresponding curve Fn for the normal metal. The difference is called the condensation energy. It is not of order kBT0 per electron; it is, in fact, much smaller, of order (where EF is the Fermi energy of the conduction electrons in the normal metal). Typically EF ~ 1 eV and kBT0 ~ 10−3 eV. Only a fraction of the metallic electrons have their energy significantly modified by the condensation process.
![Image](https://book-extracts.perlego.com/1596273/images/fig1_1-plgo-compressed.webp)
Figure 1-1
(a) The electronic specific heat C of a superconductor (in zero magnetic field) as a function of temperature (qualitative plot). Above T0 (in the normal phase) where EF is the Fermi energy. At the transition point T0, C has a discontinuity. At ≪ T0, C is roughly exponential C ~ exp (− 1.76 T0/T). (b) Free energy of the superconducting phase (FS) and of the normal phase (Fn) versus temperature. The two curves meet (with the same slope) at the transition point T = T0. At T = 0 the difference Fn – FS is of order per atom.
1–2 DIAMAGNETISM
The London Equation
We now extend our energy considerations to situations where there are supercurrents jS (r) and associated magnetic fields h(r) in the sample.1 We see that in the limit where all fields, currents, and so on, are weak and have a slow variation in space the condition of minimum free energy leads to a simple relation between fields and currents (F. and H. London, 1935).
We consider a pure metal with a parabolic conduction band; the electrons have an effective mass m. The free energy now has the following form:
(1-1) |
where FS is the energy of the electrons in the condensed state at rest and Ekin is the kinetic energy associated with the permanent currents. Let us call v(r) the drift velocity of the electrons at point r. It is related to the current density jS by
(1-2) |
(where e is the electron charge, and nS the number of superconducting electrons per cm3). Then w...
Table of contents
- Cover
- Half Title
- Title Page
- Copyright Page
- Dedication
- Table of Contents
- Chapter 1 Fundamental Properties
- Chapter 2 Magnetic Properties of First Kind Superconductors
- Chapter 3 Magnetic Properties of Second Kind Superconductors
- Chapter 4 Description of the Condensed State
- Chapter 5 The Self-Consistent Field Method
- Chapter 6 Phenomenological Landau-Ginsburg Equations
- Chapter 7 Microscopic Analysis of the Landau-Ginsburg Equations
- Chapter 8 Effects of Strong Magnetic Fields and of Magnetic Impurities
- Index
Citation styles for Superconductivity Of Metals And Alloys
APA 6 Citation
Gennes, D. (2018). Superconductivity Of Metals And Alloys (1st ed.). CRC Press. Retrieved from https://www.perlego.com/book/1596273/superconductivity-of-metals-and-alloys-pdf (Original work published 2018)
Chicago Citation
Gennes, De. (2018) 2018. Superconductivity Of Metals And Alloys. 1st ed. CRC Press. https://www.perlego.com/book/1596273/superconductivity-of-metals-and-alloys-pdf.
Harvard Citation
Gennes, D. (2018) Superconductivity Of Metals And Alloys. 1st edn. CRC Press. Available at: https://www.perlego.com/book/1596273/superconductivity-of-metals-and-alloys-pdf (Accessed: 14 October 2022).
MLA 7 Citation
Gennes, De. Superconductivity Of Metals And Alloys. 1st ed. CRC Press, 2018. Web. 14 Oct. 2022.