In this macroscopic quantum state, the electrons form. The scmaglev superconducting maglev formerly called the mlu is a magnetic levitation maglev railway system. Lecture notes applied superconductivity electrical. Superconductivity and bcs theory max planck institute. Historically, this approach has been very successful. Furthermore, bcs theory has proven unable to predict any new superconducting compounds. Consider two electrons that interact with each other via an attractive potential vr 1 r. We will then calculate and study interesting quantities of the su. More detailed accounts can be found in the excellent text books by w. Phenomenology london, ginzburglandau can obtain a uni. Bcs theory of superconductivity hyperphysics concepts. As we have seen, phonons mediate an attraction between electrons. This theory could explain the effects such as zero resistivity, meissner effect, isotopic effect etc.
Landaus theory of second order phase transition formulated in 1950, before bcs masterpiece of physical intuition grounded in thermodynamics even after bcs it still is very fruitful in analyzing the behavior of superconductors and is still one of the most widely used theory of superconductivity. The timetested bcs theory of superconductivity is generally accepted to be the correct theory of conventional superconductivity by physicists and, by extension, by the world at large. John schieffers book was written for solid state physicists with more than just a casual interest in superconductivity. Bcs theory of superconductivity the properties of type i superconductors were modeled successfully by the efforts of john bardeen, leon cooper, and robert schrieffer in what is commonly called the bcs theory. More detailed accounts can be found in the excellent text books by. The band theory of metals has been subjected to experimental tests many times and is now the accepted model of the behaviour of conductors and insulators. Bcs wave function, energy gap and quasiparticle states.
The superconducting properties of small specimens 9. Bcs theory or bardeencooperschrieffer theory is the first microscopic theory of. London and london derived a phenomenological theory of superconductivity which correctly describes the meissner e ect. Theory of superconductivity advanced books classics. New theory of superconductivity download ebook pdf, epub. But it has to be modified when it comes to superconductivity. The bcs theory is, in its simplest form, actually contradictory to our crude macroscopic view expressed earlier. Free superconductivity books download ebooks online textbooks. This site is like a library, use search box in the widget to get ebook that you want. Phonon mediated attractive interaction and the cooper pairs. In 1957, more than 40 years after the discovery of superconductivity, three physicists, bardeen, cooper and schrieffer, finally found the correct explanation to superconductivity in metals. By the di nition of magnetic work the rst law of thermodynamics for a magnetic material becomes. A key conceptual element in this theory is the pairing of electrons close to the fermi level into cooper pairs through interaction with the crystal lattice. This video lecture will explain the bcs theory of superconductivity.
Apr 16, 2017 this video lecture will explain the bcs theory of superconductivity. E physics 460 f 2000 lect 23 26 superconducting transition tc bcs prediction. As discussed earlier, superconductivity arises because electrons do not interact destructively with atoms in the crystal lattice of the material. Verify that the link points to the correct file and location. Bcs theory is unable to predict new superconductors because it assumes that superconductivity is associated with the electronphonon interaction. The reader will master london theory and the pippard equations, and go on to understand type i and type ii superconductors their thermodynamics, magnetic properties, vortex dynamics, current transport, cooper pairs and the. Hence it predicts that superconductivity and high transition temperatures will occur in materials with strong electronphonon interaction as evidenced eg by large temperature dependence of the normal. These lectures attempt at a concise description of what has been achieved so far in this direction.
We will look at features of superconductors before the discovery of the bcs theory, and examine the assumptions and methods used to develop the theory. We start with a general hamiltonian that describes manyfermion system interacting via a spinindependent. Bcs theory bcs theory of superconductor was put forward by bardeen, cooper and schrieffer in 1957 and hence named as bcs theory. Electronic structure, bcs beschreibung des supraleitenden zustands.
Theory of superconductivity problem set 10 exercise 12 diagonalization of the bcs hamiltonian. Schrieffer their surname initials providing the designation bcs to explain the behaviour of superconducting materials. Lecture notes on superconductivity a work in progress. A general theory of superconductivity with points of view differing from those of the bcs theory is presented in two parts. Superconductivity and bcs theory introduction electronphonon interaction, cooper pairs bcs wave function, energy gap and quasiparticle states predictions of the bcs theory limits of the bcs gap equation. Fernandes here we will discuss a new ground state of the interacting electron gas. The main idea of the bcs theory relies on the quantum nature of electrons. The theory describes superconductivity as a microscopic effect caused by a condensation of cooper pairs. The development of superconducting devices was greatly stimulated after the acceptance of the basic theory of superconductivity proposed in 1957 by john bardeen, leon cooper, and robert schrieffer. Bcs theory or bardeencooperschrieffer theory named after john bardeen, leon cooper, and john robert schrieffer is the first microscopic theory of superconductivity since heike kamerlingh onness 1911 discovery. The authors of the bcs theory, as it is known, received the nobel prize for their work in 1972. With the discovery of materials that went superconducting at temperatures above the theoretical limit imposed by bcs theory see history, there was and still is much debate as to what the mechanism of superconduction in these compounds might be one explanation involves the use of holes within the superconductor many high t c superconductors are.
The reduction of the energy gap as you approach the critical temperature can be taken as an indication that the charge carriers have some sort of collective nature. Each of these electrons is relatively independent and follows its own path independent of other electrons. The bcs theory says that electrons do actually interact with the atoms, but constructively. This book proposes a thorough introduction for a varied audience. The main point of the bcs theory is that the attractive electronelectron interaction mediated by the phonons gives rise to cooper pairs, i. This theory is remarkable enough that it is interesting to look at the chain of ideas which led to it. The theory is also used in nuclear physics to describe the pairing. The bcs theory has been used to successfully explain the following experi mental results. Bcs theory, in physics, a comprehensive theory developed in 1957 by the american physicists john bardeen, leon n. The theory of superconductivity introduced by ginzburg and landau is a macroscopic theory, and the bcs theory is a suitable limit to it at the microscopic scale. Bcs theory applies directly to superconductors such as nb3ge tc 23k in which the electrons are bound together by their interaction with the vibrations of the underlying lattice. Topology and geometry for physics, the fundamentals of density functional theory, the particle world of condensed matter, theory of superconductivity. Concepts of fermi liquid theory and instability of the normal state.
Robert schrieffer, which is known as the bcs theory. I outline an alternative to conventional bcs theory proposed to apply to all superconductors, conventional. A primer, microscopic theory of superconductivity, the essentials of dft and fplo, high tc superconductors. It envisions resistancefree conduction of coupled pairs of electrons called cooper pairs. Prior to this, there was ginzburglandau theory, suggested in 1950, which was a macroscopic theory. What links here related changes upload file special pages permanent link page information. Electron lattice interaction via lattice deformation. For comparison, the resistivity of copper at room temperature is. In this section, we will see how superconductivity emerges in an electron gas with attraction the theory. The data at left offer general confirmation of the bcs theory of superconductivity. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Here we will discuss a new ground state of the interacting electron gas.
The second essential observation was that superconductors not only prevent a magnetic. In the first part, a general equation for the superconductivity is. The remaining four chapters are devoted to the simplest phenomenological weak coupling theory of superconductivity on a microscopic level, the bcs theory, which provided the. Bcs theory finite temperatures the model hamiltonian bogoliubovvalatintransformation calculation of the condensation energy bcs theory having seen that the fermi sea is unstable against the formation of a bound cooper pair when the net interaction is attractive, we must then expect pairs to condense until an equilibrium point is reached. A microscopic theory of superconductivity was developed in 1957 by john bardeen, leon cooper and j. Electronic structure, bcsbeschreibung des supraleitenden zustands.
Brief introduction to superconductivity pdf 69p covered topics are discovery and first insights, the physics of the cooper pairs, bcs theory of superconductivity, characteristics of the superconducting state, the strong coupling theory, hightc superconducting materials, crystal structures, superconducting properties, models on the mechanism. Find materials for this course in the pages linked along the left. The bcs theory makes a crucial assumption at the beginning. Superconductivity and the bcs theory syed ali raza. In this work, we aim to obtain a rather general and explicit analytical result to illustrate the drivinginduced elevation of the critical temperature of a normal superconductor by extending the conventional bcs theory. Tutorial 4 the bcs theory of superconductivity june 1, 2015 in the lectures you saw a phenomenological analysis of superconductors. Levy, magnetism and superconductivity springer, 2000 1. The central feature of the bcs theory is that two electrons in the superconductor are able to form a bound pair called a cooper pair if they somehow experience an attractive interaction between. In particular, you saw that given some empirical results, many additional predictions can be made using the ginzburglandau formalism.
Free superconductivity books download ebooks online. The second order phase transition at t c ginzburg and landau, 1950. Superconductors abruptly lose all resistance to the flow of an electric current when they are cooled to temperatures near absolute zero. In a theoretical model that has since been called bcs, after their initials, they proposed the following explanation. Click download or read online button to get new theory of superconductivity book now. In typical type i superconductors, this force is due to coulomb attraction between the electron and the crystal lattice. This paper suggests the possibility that bcs theory itself as the theory of conventional superconductivity may require a fundamental overhaul. The contrasting behavior of nmr relaxation rate with ultrasound absorption is explained in a natural manner by the pair nature of bcs wave function, providing proof of this central concept of the bcs theory. The discussion of cooper pairs, the foundation for bcs theory, though not difficult to read, is easier to understand after going through gordon bayms discussion of this topic in lectures on quantum mechanics lecture notes and supplements in physics. In 1957, bardeen, cooper and schrieffer bcs proposed a theory that explained the microscopic origins of superconductivity, and could quantitatively predict the properties of superconductors. In a superconductor, the majority of these electrons merge in order to form a large collective wave. A floquet bcs gap equation is derived which calls for a numerical solution and does not permit closed analytic results. The bcs theory of superconductivity has successfully described the measured properties of type i superconductors.
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