Superconductivity is the phenomenon of certain materials exhibiting zero

electrical resistance The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual paralle ...

and the expulsion of

magnetic fields A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

below a characteristic

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

. The history of superconductivity began with Dutch

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

Heike Kamerlingh Onnes Heike Kamerlingh Onnes (21 September 1853 – 21 February 1926) was a Dutch physicist and Nobel laureate. He exploited the Hampson–Linde cycle to investigate how materials behave when cooled to nearly absolute zero and later to liquefy heliu ...

's discovery of superconductivity in mercury in 1911. Since then, many other superconducting materials have been discovered and the theory of superconductivity has been developed. These subjects remain active areas of study in the field of condensed matter physics. Johannes Diderik van der Waals

Exploring ultra-cold phenomena (to 1908)

James Dewar Sir James Dewar (20 September 1842 – 27 March 1923) was a British chemist and physicist. He is best known for his invention of the vacuum flask, which he used in conjunction with research into the liquefaction of gases. He also studied a ...

initiated research into electrical resistance at low temperatures. Dewar and

John Ambrose Fleming Sir John Ambrose Fleming FRS (29 November 1849 – 18 April 1945) was an English electrical engineer and physicist who invented the first thermionic valve or vacuum tube, designed the radio transmitter with which the first transatlantic ra ...

predicted that at absolute zero, pure metals would become perfect electromagnetic conductors (though, later, Dewar altered his opinion on the disappearance of resistance, believing that there would always be some resistance). Walther Hermann Nernst developed the

third law of thermodynamics The third law of thermodynamics states, regarding the properties of closed systems in thermodynamic equilibrium: This constant value cannot depend on any other parameters characterizing the closed system, such as pressure or applied magnetic fiel ...

and stated that absolute zero was unattainable.

Carl von Linde Carl Paul Gottfried von Linde (11 June 1842 – 16 November 1934) was a German scientist, engineer, and businessman. He discovered a refrigeration cycle and invented the first industrial-scale air separation and gas liquefaction processes, whi ...

and

William Hampson William Hampson (18541926) was the first person to patent a process for liquifying air. Early life William Hampson was born on 14 March 1854, the second son of William Hampson of Puddington, Cheshire, England.Who Was Who, Published by A&C B ...

, both commercial researchers, nearly at the same time filed for patents on the Joule–Thomson effect for the liquefaction of gases. Linde's patent was the climax of 20 years of systematic investigation of established facts, using a regenerative counterflow method. Hampson's designs was also of a regenerative method. The combined process became known as the Hampson–Linde liquefaction process. Onnes purchased a Linde machine for his research. On March 21, 1900,

Nikola Tesla Nikola Tesla ( ; ,"Tesla"
''

oscillation Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...

s by lowering the temperature, which was caused by lowered resistance. Within this patent it describes the increased intensity and duration of electric oscillations of a low temperature resonating circuit. It is believed that Tesla had intended that Linde's machine would be used to attain the cooling agents. A milestone was achieved on July 10, 1908 when

at Leiden University in the Netherlands produced, for the first time, liquified helium, which has a boiling point of 4.2

kelvin The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and phy ...

s at atmospheric pressure.

Sudden and fundamental disappearance

and Jacob Clay reinvestigated Dewar's earlier experiments on the reduction of resistance at low temperatures. Onnes began the investigations with

platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver". Pla ...

and

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile me ...

, replacing these later with mercury (a more readily refinable material). Onnes's research into the resistivity of solid mercury at cryogenic temperatures was accomplished by using

liquid helium Liquid helium is a physical state of helium at very low temperatures at standard atmospheric pressures. Liquid helium may show superfluidity. At standard pressure, the chemical element helium exists in a liquid form only at the extremely low temp ...

as a refrigerant. On April 8, 1911, 16:00 hours Onnes noted "Kwik nagenoeg nul", which translates as " esistance ofmercury almost zero." At the temperature of 4.19 K, he observed that the resistivity abruptly disappeared (the measuring device Onnes was using did not indicate any resistance). Onnes disclosed his research in 1911, in a paper titled "''On the Sudden Rate at Which the Resistance of Mercury Disappears.''" Onnes stated in that paper that the "specific resistance" became thousands of times less in amount relative to the best conductor at ordinary temperature. Onnes later reversed the process and found that at 4.2 K, the resistance returned to the material. The next year, Onnes published more articles about the phenomenon. Initially, Onnes called the phenomenon "''supraconductivity''" (1913) and, only later, adopted the term "''superconductivity.''" For his research, he was awarded the

Nobel Prize in Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...

in 1913. Onnes conducted an experiment, in 1912, on the usability of superconductivity. Onnes introduced an electric current into a superconductive ring and removed the battery that generated it. Upon measuring the electric current, Onnes found that its intensity did not diminish with the time. The current persisted due to the superconductive state of the conductive medium. In subsequent decades, superconductivity was found in several other materials; In 1913,

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

at 7 K, in 1930's niobium at 10 K, and in 1941 niobium nitride at 16 K.

Enigmas and solutions (1933–)

The next important step in understanding superconductivity occurred in 1933, when

Walther Meissner Fritz Walther Meissner (German: ''Meißner'') (16 December 1882 – 16 November 1974) was a German technical physicist. Meissner was born in Berlin to Waldemar Meissner and Johanna Greger. He studied mechanical engineering and physics at t ...

and Robert Ochsenfeld discovered that superconductors expelled applied magnetic fields, a phenomenon that has come to be known as the

Meissner effect The Meissner effect (or Meissner–Ochsenfeld effect) is the expulsion of a magnetic field from a superconductor during its transition to the superconducting state when it is cooled below the critical temperature. This expulsion will repel a ne ...

. In 1935, brothers

Fritz London Fritz Wolfgang London (March 7, 1900 – March 30, 1954) was a German physicist and professor at Duke University. His fundamental contributions to the theories of chemical bonding and of intermolecular forces ( London dispersion forces) are today ...

and

Heinz London Heinz London (Bonn, Germany 7 November 1907 – 3 August 1970) was a German-British physicist. Together with his brother Fritz London he was a pioneer in the field of superconductivity. Biography London was born in Bonn in a liberal Jewish-Ge ...

showed that the Meissner effect was a consequence of the minimization of the electromagnetic free energy carried by superconducting current. In 1950, the phenomenological

Ginzburg–Landau theory In physics, Ginzburg–Landau theory, often called Landau–Ginzburg theory, named after Vitaly Ginzburg and Lev Landau, is a mathematical physical theory used to describe superconductivity. In its initial form, it was postulated as a phenomenol ...

of superconductivity was devised by

Lev Landau Lev Davidovich Landau (russian: Лев Дави́дович Ланда́у; 22 January 1908 – 1 April 1968) was a Soviet-Azerbaijani physicist of Jewish descent who made fundamental contributions to many areas of theoretical physics. His ac ...

and

Vitaly Ginzburg Vitaly Lazarevich Ginzburg, ForMemRS (russian: Вита́лий Ла́заревич Ги́нзбург, link=no; 4 October 1916 – 8 November 2009) was a Russian physicist who was honored with the Nobel Prize in Physics in 2003, together wit ...

. The Ginzburg–Landau theory, which combined Landau's theory of second-order

phase transition In chemistry, thermodynamics, and other related fields, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states o ...

s with a Schrödinger-like wave equation, had great success in explaining the macroscopic properties of superconductors. In particular, Alexei Abrikosov showed that Ginzburg–Landau theory predicts the division of superconductors into the two categories now referred to as Type I and Type II. Abrikosov and Ginzburg were awarded the 2003

for their work (Landau having died in 1968). Also in 1950, Emanuel Maxwell and, almost simultaneously, C.A. Reynolds ''et al.'' found that the critical temperature of a superconductor depends on the isotopic mass of the constituent element. This important discovery pointed to the electron-phonon interaction as the microscopic mechanism responsible for superconductivity.

BCS theory

The complete microscopic theory of superconductivity was finally proposed in 1957 by John Bardeen, Leon N. Cooper, and Robert Schrieffer. This

BCS theory BCS theory or Bardeen–Cooper–Schrieffer theory (named after John Bardeen, Leon Cooper, and John Robert Schrieffer) is the first microscopic theory of superconductivity since Heike Kamerlingh Onnes's 1911 discovery. The theory describes sup ...

explained the superconducting current as a superfluid of

Cooper pair In condensed matter physics, a Cooper pair or BCS pair (Bardeen–Cooper–Schrieffer pair) is a pair of electrons (or other fermions) bound together at low temperatures in a certain manner first described in 1956 by American physicist Leon Coope ...

s, pairs of electrons interacting through the exchange of

phonons In physics, a phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, specifically in solids and some liquids. A type of quasiparticle, a phonon is an excited state in the quantum mechanic ...

. For this work, the authors were awarded the

in 1972. The BCS theory was set on a firmer footing in 1958, when

Nikolay Bogolyubov Nikolay Nikolayevich Bogolyubov (russian: Никола́й Никола́евич Боголю́бов; 21 August 1909 – 13 February 1992), also transliterated as Bogoliubov and Bogolubov, was a Soviet and Russian mathematician and theoretic ...

showed that the BCS wavefunction, which had originally been derived from a variational argument, could be obtained using a canonical transformation of the electronic

Hamiltonian Hamiltonian may refer to: * Hamiltonian mechanics, a function that represents the total energy of a system * Hamiltonian (quantum mechanics), an operator corresponding to the total energy of that system ** Dyall Hamiltonian, a modified Hamiltonian ...

. In 1959,

Lev Gor'kov Lev Petrovich Gor'kov (russian: Лев Петро́вич Горько́в; 14 June 1929 – 28 December 2016) was a Russian-American research physicist internationally known for his pioneering work in the field of superconductivity. He was particul ...

showed that the BCS theory reduced to the Ginzburg-Landau theory close to the critical temperature. Gor'kov was the first to derive the superconducting phase evolution equation

2eV=\hbar\frac

Little–Parks effect

The Little–Parks effect was discovered in 1962 in experiments with empty and thin-walled

superconducting Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike ...

cylinders subjected to a parallel magnetic field. The

of such cylinders shows a periodic

with the magnetic flux through the cylinder, the period being '' h''/2'' e'' = 2.07×10⁻¹⁵ V·s. The explanation provided by William Little and Ronald Parks is that the resistance oscillation reflects a more fundamental phenomenon, i.e. periodic oscillation of the superconducting critical temperature (''T''_c). This is the temperature at which the sample becomes superconducting. The Little-Parks effect is a result of collective quantum behavior of superconducting electrons. It reflects the general fact that it is the fluxoid rather than the flux which is quantized in superconductors. The Little-Parks effect demonstrates that the

vector potential In vector calculus, a vector potential is a vector field whose curl is a given vector field. This is analogous to a ''scalar potential'', which is a scalar field whose gradient is a given vector field. Formally, given a vector field v, a ''vecto ...

couples to an observable physical quantity, namely the superconducting critical temperature.

Commercial activity

Soon after discovering superconductivity in 1911, Kamerlingh Onnes attempted to make an electromagnet with superconducting windings but found that relatively low magnetic fields destroyed superconductivity in the materials he investigated. Much later, in 1955, George Yntema succeeded in constructing a small 0.7-tesla iron-core electromagnet with superconducting niobium wire windings. Then, in 1961, J. E. Kunzler, E. Buehler, F. S. L. Hsu, and J. H. Wernick made the startling discovery that at 4.2 kelvins, a compound consisting of three parts niobium and one part tin was capable of supporting a current density of more than 100,000 amperes per square centimeter in a magnetic field of 8.8 tesla. Despite being brittle and difficult to fabricate, niobium-tin has since proved extremely useful in supermagnets generating magnetic fields as high as 20 teslas. In 1962, Ted Berlincourt and Richard Hake discovered that less brittle alloys of niobium and titanium are suitable for applications up to 10 teslas. Promptly thereafter, commercial production of niobium-titanium supermagnet wire commenced at Westinghouse Electric Corporation and at Wah Chang Corporation. Although niobium-titanium boasts less-impressive superconducting properties than those of niobium-tin, niobium-titanium has, nevertheless, become the most widely used “workhorse” supermagnet material, in large measure a consequence of its very high ductility and ease of fabrication. However, both niobium-tin and niobium-titanium find wide application in MRI medical imagers, bending and focusing magnets for enormous high-energy particle accelerators, and a host of other applications. Conectus, a European consortium for superconductivity, estimated that in 2014, global economic activity, for which superconductivity was indispensable, amounted to about five billion euros, with MRI systems accounting for about 80% of that total. In 1962,

Brian Josephson Brian David Josephson (born 4 January 1940) is a Welsh theoretical physicist and professor emeritus of physics at the University of Cambridge. Best known for his pioneering work on superconductivity and quantum tunnelling, he was awarded the ...

made the important theoretical prediction that a supercurrent can flow between two pieces of superconductor separated by a thin layer of insulator. This phenomenon, now called the

Josephson effect In physics, the Josephson effect is a phenomenon that occurs when two superconductors are placed in proximity, with some barrier or restriction between them. It is an example of a macroscopic quantum phenomenon, where the effects of quantum mec ...

, is exploited by superconducting devices such as SQUIDs. It is used in the most accurate available measurements of the

magnetic flux quantum The magnetic flux, represented by the symbol , threading some contour or loop is defined as the magnetic field multiplied by the loop area , i.e. . Both and can be arbitrary, meaning can be as well. However, if one deals with the superconducti ...

''h''/2''e'', and thus (coupled with the quantum Hall resistivity) for Planck's constant ''h''. Josephson was awarded the

for this work in 1973. In 1973 found to have ''T''_c of 23 K, which remained the highest ambient-pressure ''T''_c until the discovery of the cuprate high-temperature superconductors in 1986 (see below).

High-temperature superconductors

In 1986, J. Georg Bednorz and K. Alex Mueller discovered superconductivity in a

lanthanum Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lant ...

-based cuprate

perovskite Perovskite (pronunciation: ) is a calcium titanium oxide mineral composed of calcium titanate (chemical formula ). Its name is also applied to the class of compounds which have the same type of crystal structure as (XIIA2+VIB4+X2−3), known a ...

material, which had a transition temperature of 35 K (Nobel Prize in Physics, 1987) and was the first of the

high-temperature superconductor High-temperature superconductors (abbreviated high-c or HTS) are defined as materials that behave as superconductors at temperatures above , the boiling point of liquid nitrogen. The adjective "high temperature" is only in respect to previou ...

s. It was shortly found (by Ching-Wu Chu) that replacing the lanthanum with

yttrium Yttrium is a chemical element with the symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a " rare-earth element". Yttrium is almost always found in co ...

, i.e. making

YBCO Yttrium barium copper oxide (YBCO) is a family of crystalline chemical compounds that display high-temperature superconductivity; it includes the first material ever discovered to become superconducting above the boiling point of liquid nitrogen ...

, raised the critical temperature to 92 K, which was important because liquid nitrogen could then be used as a refrigerant (at atmospheric pressure, the boiling point of nitrogen is 77 K). This is important commercially because liquid nitrogen can be produced cheaply on-site with no raw materials, and is not prone to some of the problems (solid air plugs, etc.) of helium in piping. Many other cuprate superconductors have since been discovered, and the theory of superconductivity in these materials is one of the major outstanding challenges of theoretical

condensed-matter physics Condensed matter physics is the field of physics that deals with the macroscopic and microscopic physical properties of matter, especially the solid and liquid phases which arise from electromagnetic forces between atoms. More generally, the su ...

. In March 2001, superconductivity of

magnesium diboride Magnesium diboride is the inorganic compound with the formula MgB2. It is a dark gray, water-insoluble solid. The compound has attracted attention because it becomes superconducting at 39 K (−234 °C). In terms of its composition, M ...

() was found with ''T''_c = 39 K. In 2008, the

oxypnictide In chemistry, oxypnictides are a class of materials composed of oxygen, a pnictogen (group-V, especially phosphorus and arsenic) and one or more other elements. Although this group of compounds has been recognized since 1995, interest in these co ...

iron-based superconductor Iron-based superconductors (FeSC) are iron-containing chemical compounds whose superconducting properties were discovered in 2006. In 2008, led by recently discovered iron pnictide compounds (originally known as oxypnictides), they were in the firs ...

s were discovered, which led to a flurry of work in the hope that studying them would provide a theory of the cuprate superconductors. In 2013, room-temperature superconductivity was attained in YBCO for picoseconds, using short pulses of infrared laser light to deform the material's crystal structure. In 2017 it was suggested that undiscovered superhard materials (e.g. critically doped beta-titanium Au) might be a candidate for a new superconductor with Tc, substantially higher than HgBaCuO (138 K), possibly up to 233 K, which would be higher even than H₂S. A lot of research suggests that additionally nickel could replace copper in some perovskites, offering another route to room temperature. Li+ doped materials can also be used, i.e. the spinel battery material LiTi₂O_x and the lattice pressure can increase Tc to over 13.8 K. Also LiHx has been theorized to metallise at a substantially lower pressure than H and could be a candidate for a Type 1 superconductor.

Historical publications

Papers by H.K. Onnes * "The resistance of pure mercury at helium temperatures". ''Comm. Leiden''. April 28, 1911. * "The disappearance of the resistivity of mercury". ''Comm. Leiden''. May 27, 1911. * "On the sudden change in the rate at which the resistance of mercury disappears". ''Comm. Leiden''. November 25, 1911. * "The imitation of an ampere molecular current or a permanent magnet by means of a supraconductor". ''Comm. Leiden''. 1914. BCS theory * Other key papers * * F. London and H. London, "The electromagnetic equations of the supraconductor," ''Proc. Roy. Soc. (London)'' A149, 71 (1935)
ISSN 0080-4630
* V.L. Ginzburg and L.D. Landau, ''Zh. Eksp. Teor. Fiz.'' 20, 1064 (1950) * * * A.A. Abrikosov, "On the magnetic properties of superconductors of the second group," ''Soviet Physics JETP'' 5, 1174 (1957) * * Patents * Tesla, Nikola, "''Means for Increasing the Intensity of Electrical Oscillations''", March 21, 1900.

External links and references

* Heike Kamerlingh Onnes, "
Investigations into the properties of substances at low temperatures, which have led, amongst other things, to the preparation of liquid helium
'," Nobel Lecture, December 11, 1913 * M. Tinkham, ''Introduction to Superconductivity'', 2nd Ed., McGraw-Hill, NY, 1996, * T. Shachtman, ''Absolute Zero and the Conquest of Cold'', Houghton Mifflin Co., 1999, * J. Matricon, G. Waysand and C. Glashausser, ''The Cold Wars: A History of Superconductivity'', Rutgers University Press, 2003, * J. Schmalian,
Failed theories of superconductivity
' {{DEFAULTSORT:History Of Superconductivity Superconductivity Superconductivity