The bcs theory says that electrons do actually interact with the atoms, but constructively. The main point of the bcs theory is that the attractive electronelectron interaction mediated by the phonons gives rise to cooper pairs, i. A general theory of superconductivity with points of view differing from those of the bcs theory is presented in two parts. This bcs theory explained the superconducting current as a superfluid of cooper pairs. Chernsimons theory and bcs superconductivity article in nuclear physics b 6223.

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. 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. Lecture notes on superconductivity a work in progress. Chernsimons theory and bcs superconductivity request pdf. 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. Bcs theory of driven superconductivity andreas komnik1 and michael thorwart2,3 a 1 institut f. This theory could explain the effects such as zero resistivity, meissner effect, isotopic effect etc. Due to this interaction, the electrons form bound pairs. 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. As we have seen, phonons mediate an attraction between electrons. As discussed earlier, superconductivity arises because electrons do not interact destructively with atoms in the crystal lattice of the material. A microscopic theory of superconductivity was developed in 1957 by john bardeen, leon cooper and j.

Introduction in these lectures i want to give an introduction into the physical principles of superconductivity and its fascinating properties. 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. Concepts of fermi liquid theory and instability of the normal state. 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. 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. The bcs theory reproduces the isotope effect, which is the experimental observation that for a given superconducting material, the critical temperature is inversely proportional to the mass of the isotope used in the material. 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.

Superconductivity and the bcs theory syed ali raza. Theories of superconductivity ginzburglandau theory 1950 ginzburglandau theory, named after vitaly lazarevich ginzburg and lev landau, is a mathematical theory used to model superconductivity. The bcs theory gives a complete explanation of the nuclear relaxation time in a superconductor. Theory of superconductivity, rickayzen, g wiley, new york 1965.

The second order phase transition at t c ginzburg and landau, 1950. Phenomenology london, ginzburglandau can obtain a uni. London and london derived a phenomenological theory of superconductivity which correctly describes the meissner e ect. We will then calculate and study interesting quantities of the superconducting system, and nally describe how the results predicted by the bcs theory fare against experimental evidence obtained about superconductors. By the di nition of magnetic work the rst law of thermodynamics for a magnetic material becomes. The second essential observation was that superconductors not only prevent a magnetic.

The theory describes superconductivity as a microscopic effect caused by a condensation of cooper pairs. Free superconductivity books download ebooks online textbooks. Schrieffer their surname initials providing the designation bcs to explain the behaviour of superconducting materials. Bcs theory having the above physics in mind, we postulate that as the system becomes superconducting, there is an instability toward condensation of pairs. Bcs theory definition of bcs theory by merriamwebster. The phenomena of superconductivity and superfluidity are then closely linked. For sound absorption, bcs found that one needed the distinction arose from the pair nature of the wave function and thus would not be present in a one electron theory. The scmaglev superconducting maglev formerly called the mlu is a magnetic levitation maglev railway system. Cooper problem ii 3 orbital part of the wave function spin singlet. Oct 25, 2007 macroscopic theory of superconductivity valid for magnetic fields of arbitrary magnitude and the behaviour of superconductors in weak high frequency fields are discussed. This video lecture will explain the bcs theory of superconductivity. 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. For comparison, the resistivity of copper at room temperature is.

Robert schrieffer, which is known as the bcs theory. Our grand tour of many body theories continues with bardeen, cooper and schrieffers bcs theory of superconductivity, based on the idea that electrons in a superconductor bind to form cooper pairs that behave like bosons. Macroscopic theory of superconductivity valid for magnetic fields of arbitrary magnitude and the behaviour of superconductors in weak high frequency fields are discussed. But it has to be modified when it comes to superconductivity. Bcs theory is unable to predict new superconductors because it assumes that superconductivity is associated with the electronphonon interaction. Bcs theory of superconductivity hyperphysics concepts. 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. 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 them. The bcs theory has been used to successfully explain the following experi mental results.

Introduction superconductivity discovered in 1911 by onnes 9, is the quantum phenomena that certain materials exhibit under particular magnetic and temperature regimes. 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. Lecture notes applied superconductivity electrical. Bcs theory showed that the basic interaction responsible for superconductivity appears to be that of a pair of electrons by means of an interchange of virtual phonons. The bcs theory is, in its simplest form, actually contradictory to our crude macroscopic view expressed earlier. The superconducting properties of small specimens 9. It envisions resistancefree conduction of coupled pairs of electrons called cooper pairs. The data at left offer general confirmation of the bcs theory of superconductivity. In this section, we will see how superconductivity emerges in an electron gas with attraction the theory. 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 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. The authors of the bcs theory, as it is known, received the nobel prize for their work in 1972. In particular, you saw that given some empirical results, many additional predictions can be made using the ginzburglandau formalism. Electron lattice interaction via lattice deformation.

More detailed accounts can be found in the excellent text books by w. Eremin, maxplanck institut fur physik komplexer systeme, dresden, germany. There existed no consistent microscopic theory that described why superconductivity arose, from the time it was dis. Bcs theory of superconductivity john bardeen leon neil cooper john robert schrieffer of the prize of the prize of the prize usa usa usa university of illinois urbana, il, usa brown university providence, ri, usa university of pennsylvania philadelphia, pa, usa b. The problem of formulating a microscopic theory of superconductivity is also considered. Historically, this approach has been very successful. Superconductors abruptly lose all resistance to the flow of an electric current when they are cooled to. Free superconductivity books download ebooks online. Superconductivity and the bcs theory mapping ignorance.

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. Prior to this, there was ginzburglandau theory, suggested in 1950, which was a macroscopic theory. Below the transition, the superconductor speci c heat shows activated behavior, as if there is. This theory is based on the idea that there is an attractive interaction between electrons caused by the phonons. Aug 18, 2010 bcs theory showed that the basic interaction responsible for superconductivity appears to be that of a pair of electrons by means of an interchange of virtual phonons.

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. Phonon mediated attractive interaction and the cooper pairs. This superconducting state is called the bcs state and the hamiltonian they dealt with is called the bcs hamiltonian. The speci c heat of a superconductor c s and and normal metal c n. Bcs theory bcs theory of superconductor was put forward by bardeen, cooper and schrieffer in 1957 and hence named as bcs theory.

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