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. A second feature of superconductivity reasonably explained by bcs theory is the meissner effect the complete expulsion of all magnetic fields from the interior of the superconductor. Chernsimons theory and bcs superconductivity request pdf. As we have seen, phonons mediate an attraction between electrons. Macroscopic theory of superconductivity valid for magnetic fields of arbitrary magnitude and the behaviour of superconductors in weak high frequency fields are discussed. Bcs theory of superconductivity hyperphysics concepts. In typical type i superconductors, this force is due to coulomb attraction between the. This theory is remarkable enough that it is interesting to look at the chain of ideas which led to it. Robert schrieffer, which is known as the bcs theory. By the late 1970s, superconductivity seemed to be a more or less closed subject. 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.
Superconductivity and the bcs theory mapping ignorance. However as pointed out by chapnik many years ago, superconductors seem to care a lot about whether the carriers are electrons or holes. Bcs theory having the above physics in mind, we postulate that as the system becomes superconducting, there is an instability toward condensation of pairs. A microscopic theory of superconductivity was developed in 1957 by john bardeen, leon cooper and j. The exactly solvable bcs hamiltonian of superconductivity is considered from several viewpoints. Elaboration of the model derived from the bcs theory of superconductivity to cite this article. Lecture notes applied superconductivity electrical. M2icfp 20172018 the bcs theory of superconductivity bardeen. Lecture notes on superconductivity a work in progress. Electron lattice interaction via lattice deformation.
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. The authors of the bcs theory, as it is known, received the nobel prize for their work in 1972. Prior to this, there was ginzburglandau theory, suggested in 1950, which was a macroscopic theory. The bcs theory has been used to successfully explain the following experi mental results. Since the theory of bcs, this has been confirmed by the direct observation of the quantization of the magnetic flux within a hollow superconductivity cylinder. The speci c heat of a superconductor c s and and normal metal c n.
The second order phase transition at t c ginzburg and landau, 1950. More detailed accounts can be found in the excellent text books by w. 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. Here we will discuss a new ground state of the interacting electron gas. 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. In this macroscopic quantum state, the electrons form.
Hamiltonian of fermionic quasiparticle excitations that interact via a weak at tractive interaction. Superconductivity and bcs theory max planck institute. The microscopic theory of superconductivity by bardeen, cooper and schrieffer bcs is considered one of the most successful theories in condensed matter. The theory describes superconductivity as a microscopic effect caused by a condensation of cooper pairs. By the di nition of magnetic work the rst law of thermodynamics for a magnetic material becomes. The data at left offer general confirmation of the bcs theory of superconductivity. This video lecture will explain the bcs theory of superconductivity. Bcs theory fails to explain high temperature superconductivity because electronphonon coupling cannot be made strong enough and more importantly because the hightc superconductors lack a fermi surface just above tc. Bcs wave function, energy gap and quasiparticle states. Bcs theory definition of bcs theory by merriamwebster. Bcs bardeencooperschrieffer theory is essentially just hartreefock theory lec. Bcs theory, in physics, a comprehensive theory developed in 1957 by the american physicists john bardeen, leon n. 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.
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. In this section, we will see how superconductivity emerges in an electron gas with attraction the theory. Mathematical background and derivation of the bcs functional 5 2. Richardsons ansatz, conformal field theory, integrable inhomogenous vertex models and. 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. Schrieffer their surname initials providing the designation bcs to explain the behaviour of superconducting materials. Find materials for this course in the pages linked along the left. The bcs theory of superconductivity has successfully described the measured properties of type i superconductors.
Bcs theory bcs theory of superconductor was put forward by bardeen, cooper and schrieffer in 1957 and hence named as bcs theory. Bcs theory of driven superconductivity andreas komnik1 and michael thorwart2,3 a 1 institut f. Why does bcs theory fail to explain superconductivity at high. This theory could explain the effects such as zero resistivity, meissner effect, isotopic effect etc. Introduction to the theory of superconductivity pdf 82p. 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. Below the transition, the superconductor speci c heat shows activated behavior, as if there is. The superconducting properties of small specimens 9. 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. 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.
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. Phonon mediated attractive interaction and the cooper pairs. This creates a state of perfect diamagnetism, with susceptibility. Suppose an electron approaches a positive ion core.
The cooper pairs in a conventional bulk superconductor. Bcs theory doesnt know the difference between electrons and holes, it treats them as equivalent quasiparticles. Eremin, maxplanck institut fur physik komplexer systeme, dresden, germany. 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. Introduction in these lectures i want to give an introduction into the physical principles of superconductivity and its fascinating properties. 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. Fernandes here we will discuss a new ground state of the interacting electron gas. A general theory of superconductivity with points of view differing from those of the bcs theory is presented in two parts. The bcs theory makes a crucial assumption at the beginning.
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. The bcs theory says that electrons do actually interact with the atoms, but constructively. Richardsons ansatz, conformal field theory, integrable inhomogenous vertex models and chernsimons. It was well understood based on the bcs theory and extensions thereof that. 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. Superconductivity and the bcs theory syed ali raza. Apr 16, 2017 this video lecture will explain the bcs theory of superconductivity. Concepts of fermi liquid theory and instability of the normal state. More detailed accounts can be found in the excellent text books by.
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