Reference › History of superconductivity

History of superconductivity

68 sources, listed at the end · last revised 7 October 2026

The history of superconductivity begins in 1911, when Heike Kamerlingh Onnes's laboratory in Leiden found that mercury loses its electrical resistance near 4.2 K (−269 °C).^[1] In the 115 years since, the highest reproduced transition temperature (T_c), the temperature below which a material superconducts, has reached 133 to 138 K at ambient pressure (one atmosphere) in copper oxides, and about 250 K in a hydrogen-rich compound at about 170 gigapascals (GPa), or 1.7 million atmospheres.^[7][8][9]

The record rose by less than 20 K in the 62 years to 1973 and by less than 1 K in the next 13. It then rose by about 110 K between 1986 and 1993, after superconductivity was found in copper oxides.^[10][4][7] A microscopic theory of the effect was published in 1957, 46 years after the discovery.^[3]

No material is known to superconduct at room temperature and ambient pressure. Two papers reporting room-temperature superconductivity under pressure were retracted in 2022 and 2023, and reports of 298 K at 260 GPa (2025) and of 151 K at ambient pressure (2026) have not been independently reproduced.^{[11][12][13][14]}

Discovery in Leiden

On 10 July 1908 Kamerlingh Onnes liquefied helium for the first time, which made temperatures a few kelvin above absolute zero available for experiments.^[1] On 8 April 1911 he wrote in his notebook that the resistance of mercury cooled with liquid helium was "practically zero" at about 3 K, and a plot of measurements made on 26 October 1911 shows the resistance dropping abruptly at 4.20 K.^[1]

The Leiden group reported in 1913 that lead and tin also superconduct, near 6 K and 4 K.^[1] The accepted value for lead is 7.2 K.^[15] In September 1913 Kamerlingh Onnes predicted that superconducting coils would generate fields of 10 tesla (T).^[16] In January 1914 his laboratory found that a field of 0.06 T, about 170 times weaker, returned lead at 4.25 K to its normal, resistive state.^[1]

Magnetic behavior and theory

In 1933 Walther Meissner and Robert Ochsenfeld found that a metal cooled below its transition in a magnetic field expels the field from its interior.^[2][16] This Meissner effect is, with zero resistance, one of the two properties by which a superconductor is identified (see Verifying a superconductor).^[5] Two years later the brothers Fritz and Heinz London published electromagnetic equations for a superconductor, now called the London equations, which give the depth to which a magnetic field enters the surface.^[17][16]

In 1950 Vitaly Ginzburg and Lev Landau published a phenomenological theory, one that describes the superconducting state mathematically without deriving it from the behavior of individual electrons.^[16][18] In the same year two independent studies of mercury found that samples made of heavier isotopes have a lower T_c.^[19][20][15] Isotopes of an element differ only in the mass of the nucleus, and heavier nuclei vibrate more slowly, so this isotope effect tied superconductivity to the vibrations of the crystal lattice.^[15][21]

The microscopic theory came in 1957 from John Bardeen, Leon Cooper and J. Robert Schrieffer.^[3] In BCS theory, named from their initials, the lattice vibrations, called phonons, bind electrons into Cooper pairs, and the paired electrons move without resistance.^[21] Breaking a pair takes a minimum energy, the energy gap.^[21] In 1960 Ivar Giaever gave direct evidence of the gap by tunneling, the passage of electrons through a thin insulating layer between two metals.^[22]

Also in 1957 Alexei Abrikosov used Ginzburg-Landau theory to describe type II superconductors.^[18][15] These admit a magnetic field in thin tubes called vortices and remain superconducting in high fields, whereas type I materials expel the field completely.^[18][15] The superconductors in technical use are type II.^[18] L. V. Shubnikov's group in Kharkov had measured the two critical fields of such a material in the mid-1930s.^[16]

In 1962 Brian Josephson predicted that a supercurrent, a current that flows with no voltage, can pass through a thin insulating barrier between two superconductors, an arrangement now called a Josephson junction.^[23][22] A probable observation of the effect was published in March 1963, and later experiments confirmed it.^[24][22] The junction is the working element of the superconducting quantum interference device (SQUID), a detector of magnetic fields down to about 10⁻¹⁴ T (see Applications of superconductors),^[25] and experiments of 1984 and 1985 on a circuit containing one were recognized by the 2025 Nobel Prize in Physics.^[26]

Niobium compounds and the first magnets

Walther Meissner's group at the Physikalisch-Technische Reichsanstalt near Berlin found superconductivity in niobium in 1930.^[27][16] Its T_c of 9.2 K is the highest of any chemical element at ambient pressure.^[16][15] Niobium nitride followed in 1941 at about 15 K.^[16] In 1953 a Bell Laboratories group reached 17.9 K in NbN-NbC, niobium nitride combined with niobium carbide, and a University of Chicago group found 17 K in V₃Si, which has the crystal structure called A15.^[16] In 1954 Bell Laboratories reported 18 K in Nb₃Sn, another of the A15 compounds, a family of more than 60 materials that share this cubic structure.^[16][10]

The first successful superconducting magnet, wound from niobium wire in 1954, produced 0.71 T.^[16] In 1961 Nb₃Sn was shown to carry a high current density in a field of 8.8 T.^[28] Niobium-titanium alloy later became the dominant commercial superconductor, and Nb₃Sn is still chosen where high critical currents are needed in high magnetic fields (see Applications of superconductors).^[16][10]

Thin films of Nb₃Ge reached 22.3 K in 1973 and about 23 K a year later.^[10] A15 compounds held the record for 32 years, until 1986.^[10]

Heavy-fermion and organic superconductors

In 1979 Frank Steglich and colleagues reported superconductivity at about 0.5 K in CeCu₂Si₂.^[29] The compound was the first heavy-fermion superconductor, a metal whose conduction electrons behave as if they were about 200 times heavier than free electrons.^[29][30] In 1980 a group at Orsay reported the first organic superconductor, one made of carbon-based molecules: the salt (TMTSF)₂PF₆, where TMTSF stands for tetramethyltetraselenafulvalene, synthesized by Klaus Bechgaard in Copenhagen.^[31][32] It superconducts below 0.9 K at a pressure of 12 kilobar (1.2 GPa, about 12,000 atmospheres).^[31][33]

Both materials superconduct close to a magnetically ordered state, in which the electrons' magnetic moments line up in a regular pattern.^[34][35] Interest in pairing produced by magnetic interactions between electrons, in place of phonons, dates from the 1979 discovery.^[36] Whether such pairing operates in either material is not settled: a 2017 study found that the energy gap of CeCu₂Si₂ does not change sign, whereas magnetic pairing is expected to give a gap that does,^[36] and a 2003 review reports controversy over the nature of the superconducting state in the organic salts.^[33] Superconductors whose pairing is thought to come from something other than the phonon mechanism of BCS theory are called unconventional, and the others conventional.^[37]

Cuprates

In April 1986 Georg Bednorz and Alex Müller of the IBM research laboratory in Zurich submitted a paper reporting a sharp fall in the resistance of an oxide of lanthanum, barium and copper.^[4] Its onset, the temperature at which the resistance begins to fall, was about 35 K, 12 K above the Nb₃Ge record.^[4][5]

In early 1987 M. K. Wu and colleagues reported 93 K (−180 °C) in another copper oxide, or cuprate, now written YBa₂Cu₃O₇.^[6] It was the first superconductor with a T_c above the boiling point of liquid nitrogen, 77 K (−196 °C), a cheaper coolant than the liquid helium that earlier superconductors needed.^[38][5] In 1988 a bismuth cuprate reached about 105 K and a thallium cuprate 125 K.^[39][40] In 1993 the mercury cuprate HgBa₂Ca₂Cu₃O_8+δ, known as Hg-1223, reached 133 K (−140 °C); δ is a small, variable excess of oxygen.^[7] Replacing part of the mercury with thallium gave 138 K in 1995.^[8] In 2026 the mercury cuprates still held the record for a stable material at ambient pressure.^[14]

In 1994 a resistive onset of 164 K was measured in Hg-1223 under 31 GPa (about 300,000 atmospheres).^[41][14] No material showed a higher T_c until 2015.^[42]

The pairing in the cuprates is widely thought to come from something other than phonons, with magnetic interactions the candidate most widely considered, and a rigorous theory of it has not been established.^[36][37] Experiments have largely settled that the pairs have d-wave symmetry, in which the pair state changes sign with direction in the crystal.^[43]

Fullerides, magnesium diboride, iron and nickel compounds

Four more groups of superconductors found between 1991 and 2019 have lower maximum transition temperatures than the cuprates; Superconducting materials describes them. In 1991 C₆₀, a solid built from 60-atom carbon cages, was found to superconduct at 18 K when doped with potassium, that is, with potassium atoms added, and a cesium-rubidium compound of the same kind at 33 K.^[44][45] In 2001 Jun Akimitsu's group reported 39 K in magnesium diboride, MgB₂.^[46][38]

In 2008 Hideo Hosono's group reported 26 K in a fluorine-doped lanthanum iron arsenide.^[47] Related iron-based superconductors reached 55 to 56 K in the same year.^[48][49]

Superconductivity in a nickel oxide, or nickelate, was reported in 2019: thin films of Nd_0.8Sr_0.2NiO₂ superconduct at 9 to 15 K.^[50] In 2023 crystals of La₃Ni₂O₇ showed signs of superconductivity near 80 K at pressures of 14 to 43.5 GPa,^[51] and crystals with samarium in place of part of the lanthanum reached an onset of 96 K under pressure in a 2026 report.^[52] Thin films of related nickelates superconduct at ambient pressure, with an onset of about 63 K and zero resistance at about 37 K reported in 2026.^[53][54]

Hydrides under pressure

In 2004 Neil Ashcroft argued that hydrogen-rich compounds, or hydrides, could be high-temperature superconductors at pressures within reach of the diamond anvil cell, a device that squeezes a sample between the tips of two diamonds.^[55] In 1968 he had proposed the same of metallic hydrogen.^[56]

In 2015 a group in Mainz reported a T_c of 203 K (−70 °C) in hydrogen sulfide compressed to 155 GPa, where it forms H₃S.^[42] A calculation published in 2014 had given 191 to 204 K at 200 GPa for a compound of the same composition, written (H₂S)₂H₂.^[57] The T_c was lower when hydrogen was replaced by its heavier isotope deuterium, as expected of a conventional superconductor.^[42] Other laboratories have reproduced the transition.^[58]

In 2018 two groups reported superconductivity in LaH₁₀, a lanthanum superhydride, meaning a hydride unusually rich in hydrogen. One saw resistance drops beginning near 260 K at about 190 GPa.^[59] The other measured zero resistance and an isotope effect, with a T_c of about 250 K (−23 °C) at about 170 GPa, and published the result in 2019.^[9] A third group reproduced the 250 K value in 2020 on samples of up to 10 by 20 micrometers, and it is the highest T_c confirmed by independent laboratories.^[60]

Retracted claims and unreproduced reports

Two reports of superconductivity at room temperature were published in Nature and later retracted. The first, of 2020, described a carbonaceous sulfur hydride at 288 K and 267 GPa and was retracted on 26 September 2022.^[11] The second, of 2023, described a nitrogen-doped lutetium hydride at 294 K and 1 GPa and was retracted on 7 November 2023.^[12] Both came from one group at the University of Rochester, and a university investigation concluded that its leader had fabricated data.^[11][12][61] Also in 2023, two preprints claimed superconductivity at 400 K (127 °C) or above at ambient pressure in LK-99, a copper-substituted lead apatite (a lead phosphate).^[62][63] The resistance drop was traced to a copper sulfide impurity, and pure crystals proved to be insulators.^[64][65]

A preprint of September 2025 reported resistive onsets of up to 298 K (25 °C) at 260 GPa in the hydride LaSc₂H₂₄.^[13] In 2026 a second group reported seven unsuccessful attempts to make the compound.^[66]

In March 2026 a University of Houston group reported that Hg-1223 compressed to between 10 and 30 GPa, then released at 4.2 K, kept a resistive onset of up to 151 K at ambient pressure.^[14] The state is metastable and its T_c falls on warming. Zero resistance was not reported, and no other group has reproduced the result.^[14]

Record transition temperatures

The table lists the main steps in the record. Smaller steps are left out.

Nobel Prizes

The table lists the Nobel Prizes in Physics awarded for work on superconductivity or on circuits that depend on it.

The 1913 citation does not mention superconductivity.^[67] Bardeen had also received the 1956 prize and is the only person awarded the physics prize twice.^[68] The 1987 prize was announced 18 months after Bednorz and Müller submitted their paper.^[5][4] Leggett's share of the 2003 prize was for the theory of superfluid helium-3.^[18]

See also

• Superconductivity
• Superconducting materials
• High-pressure hydrides
• Claims of room-temperature superconductivity
• Verifying a superconductor
• Room-temperature superconductor

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