Superconductors cannot be penetrated by magnetic flux lines

Magnetic flux

Magnetic flux , is a measure of the amount of magnetic B field passing through a given surface . The SI unit of magnetic flux is the weber...

 (Meissner–Ochsenfeld effect). This Meissner state breaks down when the applied magnetic field is too large. Superconductors can be divided into two classes according to how this breakdown occurs. In Type-I superconductors, superconductivity is abruptly destroyed via a first order phase transition when the strength of the applied field rises above a critical value H_c. As such, they have only a single critical magnetic field at which the material ceases to superconduct, becoming resistive. Depending on the geometry of the sample, one may obtain an intermediate state described first by Lev Landau

Lev Landau

Lev Davidovich Landau was a prominent Soviet physicist who made fundamental contributions to many areas of theoretical physics...

  consisting of a baroque pattern

Husimi Q representation

The Husimi-Q distribution is a mathematical tool used in physics, and was introduced in 1940. The Q-representation is a quasi-probability distribution commonly used in quantum mechanics and also to represent the quantum state of light. It is used in the field of quantum optics and particularly...

 of macroscopically large regions of normal material carrying a magnetic field mixed with regions of superconducting material containing no field. Elementary

Chemical element

A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...

 superconductors, such as aluminium

Aluminium

Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 and lead

Lead

Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 are typical Type-I superconductors. The origin of their superconductivity is explained by BCS theory

BCS theory

BCS theory — proposed by Bardeen, Cooper, and Schrieffer in 1957 — is the first microscopic theory of superconductivity since its discovery in 1911. The theory describes superconductivity as a microscopic effect caused by a "condensation" of pairs of electrons into a boson-like state...

.
This type of superconductivity is normally exhibited by pure metals, e.g. aluminium, lead or mercury.

See also

• Conventional superconductor
  Conventional superconductor
  Conventional superconductors are materials that display superconductivity as described by BCS theory or its extensions.Critical temperatures of some simple metals:ElementTc Al1.20Hg4.15Mo0.92Nb9.26Pb7.19...
  
  
• Covalent superconductors
  Covalent superconductors
  Covalent semiconductors are such solids as diamond, silicon, germanium, silicon carbide and silicon-germanium where atoms are linked by covalent bonds. Most of those materials, at least in their bulk form, are well studied and rarely hit the front pages of the top scientific journals in the last...
  
  
• List of superconductors
• High-temperature superconductivity
  High-temperature superconductivity
  High-temperature superconductors are materials that have a superconducting transition temperature above . From 1960 to 1980, 30 K was thought to be the highest theoretically possible Tc...
  
  
• Room temperature superconductor
  Room temperature superconductor
  A room-temperature superconductor is a material yet to be discovered which would be capable of exhibiting superconducting properties at operating temperatures above 0° C . This is not strictly speaking "room temperature" A room-temperature superconductor is a material yet to be discovered...
  
  
• Superconductivity
  Superconductivity
  Superconductivity is a phenomenon of exactly zero electrical resistance occurring in certain materials below a characteristic temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum...
  
  
• Superconductor classification
  Superconductor classification
  Superconductors can be classified in accordance with several criteria that depend on our interest in their physical properties, on the understanding we have about them, on how expensive is cooling them or on the material they are made of....
  
  
• Technological applications of superconductivity
  Technological applications of superconductivity
  Some of the technological applications of superconductivity include:* the production of sensitive magnetometers based on SQUIDs* fast digital circuits ,...
  
  
• Timeline of low-temperature technology
  Timeline of low-temperature technology
  The following is a timeline of low-temperature technology and cryogenic technology .-16th century BCE – 17th century CE :...
  
  
• Type-1.5 superconductivity
• Type-II superconductor
  Type-II superconductor
  A Type-II superconductor is a superconductor characterized by the formation of vortex lattices in magnetic field. It has a continuous second order phase transition from the superconducting to the normal state within an increasing magnetic field....
  
  
• Unconventional superconductor
  Unconventional superconductor
  Unconventional superconductors are materials that display superconductivity which does not conform to either the conventional BCS theory or the Nikolay Bogolyubov's theory or its extensions....