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Room-temperature superconductor

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

A room-temperature superconductor is a material that would conduct electricity with zero resistance and expel magnetic fields at about 293 to 300 kelvin (K), or 20 to 27 °C, and at one atmosphere of pressure. No such material is known. The highest critical temperature (T_c), the temperature below which a material superconducts, found in a stable material at one atmosphere is 133 to 138 K (about −140 to −135 °C), in mercury-based copper oxides: 133 K in a compound discovered in 1993, and 138 K when part of its mercury is replaced by thallium.^[1][2]

Higher reproduced values have been reached only under high pressure. Lanthanum hydride, LaH₁₀, a hydrogen-rich compound, superconducts at about 250 K (−23 °C) when squeezed to about 170 gigapascals (GPa), roughly 1.7 million atmospheres.^[3] Reports of superconductivity at 288 to 400 K made between 2020 and 2023 were retracted or refuted, and a 2025 report of 298 K at 260 GPa has not been reproduced.^{[9][10][11][5][6]}

No accepted physical law forbids a room-temperature superconductor, and no accepted theory predicts a material that would be one. Research follows four routes: hydrogen-rich compounds that might survive at low pressure, copper and nickel oxides, high-pressure states frozen in by a rapid release of pressure, and computer searches of candidate crystals. A material that worked would remove the cooling plant that superconducting magnets and cables depend on, provided it could also carry large currents in a magnetic field.

Definition

A superconductor loses all electrical resistance and expels magnetic fields (the Meissner effect) when cooled below its critical temperature. Heike Kamerlingh Onnes found the first, mercury, in Leiden in 1911, with a critical temperature of 4.2 K (−269 °C).^[7][8] The pressure half of the definition is ambient pressure: one standard atmosphere, 101,325 pascals, which is about 0.0001 GPa.^[13]

The pressure condition matters because the term is also applied to materials that reach these temperatures only at megabar pressures (1 megabar is 100 GPa, about a million atmospheres). A retracted 2020 paper and a 2025 preprint, a paper posted before peer review, both carry "room-temperature superconductivity" in their titles for results at 267 GPa and 260 GPa.^[9][5] For scale, the pressure at the center of the Earth is about 364 GPa.^[14] Such pressures are produced in a diamond anvil cell, which squeezes a sample between the tips of two diamonds.^[14] The LaH₁₀ crystals in one confirming experiment, grown and measured inside such a cell, were at most 10 by 20 micrometers (0.01 by 0.02 millimeters) in size.^[4] A material that exists only in that condition cannot be drawn into a wire or wound into a magnet, so for practical purposes a room-temperature superconductor has to work at one atmosphere.

Where the record stands

At one atmosphere the record belongs to a cuprate, a copper oxide superconductor: HgBa₂Ca₂Cu₃O_8+δ (Hg-1223) reached 133 K in 1993, and 138 K in 1995 with part of its mercury replaced by thallium.^[1][2] That is less than half of room temperature on the absolute scale, and a 2026 paper still gives the 1993 value as the record.^[15] The same paper, from one group, reports that Hg-1223 compressed to 10 to 30 GPa and then decompressed at 4.2 K kept a resistive onset, the temperature at which the resistance starts to fall, of up to 151 K at one atmosphere. Zero resistance in that state was not reported. A sample recovered from the cell showed magnetic shielding below about 140 K. Cycling a quenched sample up to room temperature lowered its onset from 147 K to 143 K.^[15] The result has not been independently reproduced. Among conventional superconductors, in which vibrations of the crystal lattice bind the electrons into pairs, the accepted record at one atmosphere is 39 K, in magnesium diboride (MgB₂).^[16][17]

Under pressure, Hg-1223 reached an onset of 164 K at 31 GPa in 1994.^[18][15] Hydrogen-rich compounds then took the record: the sulfur hydride H₃S at 203 K and 155 GPa in 2015, and LaH₁₀ at about 250 K and about 170 GPa in 2019, each with zero resistance, a shift of T_c when hydrogen is replaced by its heavier isotope deuterium (the isotope effect), and a lower T_c in a magnetic field.^[12][3] Another group had reported a drop in resistance beginning near 260 K in LaH₁₀ at about 190 GPa in 2018, and a third measured a transition at about 250 K in 2020.^[19][4] Magnetic measurements showing that both compounds screen an applied field followed in 2022.^[20] A comment published in December 2024 by fifteen physicists holds that hydride superconductivity is real; Jorge Hirsch disputes this, arguing that the magnetic evidence is unreliable.^[21][22]

A 2025 preprint reports resistive onsets up to 298 K at 260 GPa in the lanthanum scandium hydride LaSc₂H₂₄, and zero resistance in two cells, with no measurement of magnetization or susceptibility.^[5] A second group made seven attempts to synthesize the compound at 250 to 280 GPa, did not obtain it, and found no superconductivity between 245 and 300 K in the four cells that gave resistance data.^[6] The full chronology is in History of superconductivity, and current values are kept on the current record page.

What a material would need

A superconductor at 300 K and one atmosphere has to meet three conditions.

Its electrons must stay paired up to at least 300 K. Electrons in a superconductor bind into Cooper pairs, and heat breaks the pairs above a temperature set by the strength of the binding. In a conventional superconductor, where the binding comes from lattice vibrations (phonons), T_c is the temperature at which pairs form.

The pairs must also share one quantum state across the sample (phase coherence) up to at least 300 K. Their resistance to being knocked out of step is called the superfluid stiffness, and it grows with the density of superconducting carriers. Victor Emery, Steven Kivelson and coauthors expressed the two requirements as two temperatures: the one at which pairs form, and the one up to which the stiffness can keep the pairs in step. T_c is limited by the lower of the two.^[23] In their tabulation the stiffness temperature of lead is about 600,000 K against a T_c of 7.2 K, and that of MgB₂ is 1,400 K against 39 K, so in these materials pairing sets T_c.^[23] For Hg-1223 the stiffness temperature is 130 to 190 K, close to its T_c, while the pairing temperature is 435 K if the measured energy gap, the energy needed to break a pair, is taken as a measure of pairing.^[23] Part of the gap measured in cuprates, the pseudogap, may not come from pairing: one study puts the onset of pair formation at about 130 to 150 K.^[24] Both temperatures are estimates, and models exist in which T_c exceeds any fixed multiple of the stiffness.^[23][25]

The crystal structure that hosts the pairs must exist and last at one atmosphere. It can be the stable form of the compound or a metastable one that persists as diamond does. About half of 29,902 known inorganic crystalline phases examined in one survey are metastable.^[26]

Whether it is possible

No accepted theorem rules out superconductivity at 300 K and one atmosphere, and no accepted theory predicts a material that has it.^[27][17][28] Most published limits concern phonon-mediated pairing, the mechanism in H₃S, whose T_c was calculated before its measurement was published.^[29][12]

In 1964 William Little argued from the pairing theory of the time that a suitably built organic polymer should superconduct well above room temperature.^[30] Until the hydride discoveries, statements persisted in the literature that theory capped T_c at around 40 K. They rested on McMillan's formula of 1968, fitted only to moderately strong coupling between electrons and phonons; Allen and Dynes showed in 1975 that the theory behind it sets no such ceiling.^[27][31][32] Trachenko and coauthors derive from fundamental constants a ceiling on how fast atoms can vibrate, and from it an upper limit on phonon-mediated T_c of the order of 100 to 1,000 K, a range that includes room temperature.^[33] Semenok, Altshuler and Yuzbashyan argue that a crystal becomes unstable when the coupling between its electrons and lattice vibrations grows too strong, and that room-temperature phonon-mediated superconductivity is feasible only in hydrogen compounds.^[34]

A 2025 survey by Gao and coauthors calculated T_c at one atmosphere for more than 20,000 metals and found that high vibration frequency and strong pairing rarely occur in the same compound. The compounds with the highest calculated T_c, the hypothetical Li₂AgH₆ and Li₂AuH₆, reach 83 to 116 K depending on the method and lie 319 and 172 millielectronvolts (meV) per atom above the convex hull, meaning they are calculated to be unstable against decomposition. The authors write that physical laws do not strictly limit T_c and judge room-temperature conventional superconductivity at ambient pressure "extremely unlikely".^[17]

For unconventional superconductors such as the cuprates, where phonons are not thought to bind the pairs, no calculation of comparable reliability exists.^[28][35] A 2025 numerical study of simplified models by Qin and Yang finds T_c limited to 4 to 7% of the pairing interaction energy. Room temperature would then need an interaction beyond 400 to 700 meV, which the authors consider unrealistic for known materials.^[36]

Routes being pursued

Hydrogen-rich compounds

Hydrogen atoms are the lightest and vibrate fastest, which favors phonon-mediated pairing. Neil Ashcroft argued in 1968 that hydrogen compressed into a metal could superconduct at high temperature, and proposed in 2004 that hydrogen-rich compounds (hydrides) could do so at pressures well below those needed for pure hydrogen.^[37][38] H₃S and LaH₁₀ confirmed the idea at megabar pressures. Current work tries to keep the high T_c at lower pressure. LaBeH₈ superconducts at 110 K at 80 GPa.^[39] Mg₂IrH₆ was predicted to superconduct at one atmosphere, at 65 to 170 K depending on the calculation, and attempts to make it produced the insulator Mg₂IrH₅.^[40][41][42] Its relative Mg₂RhH₆ was made in 2026 and superconducts at 24 to 29 K between 30 and 53 GPa.^[43] See High-pressure hydrides.

Cuprates and nickelates

Cuprates, layered copper oxides found to superconduct in 1986 without having been predicted, have held the record at one atmosphere since then.^[44][28] Yttrium barium copper oxide, YBa₂Cu₃O₇, reached 93 K in 1987, above the 77 K boiling point of liquid nitrogen.^[45] Nickelates, nickel oxides with related layered structures, were found to superconduct in 2019, at 9 to 15 K in thin films. Later reports include signs of superconductivity near 80 K in La₃Ni₂O₇ above 14 GPa in 2023, an onset of 92 K with zero resistance at 73 K in a samarium-substituted crystal at about 22 GPa (published 2026), and, at one atmosphere, an onset near 63 K with zero resistance near 37 K in thin films strained by the crystal they are grown on.^{[46][47][48][49]} See Superconducting materials.

Pressure quenching

Some states created under pressure survive if the pressure is released quickly at low temperature (a pressure quench). A group at the University of Houston used the method on iron selenide (FeSe), which superconducts at 9 K, and retained a T_c of about 37 K at one atmosphere, in a state that was stable only up to about 200 K.^[50] The same group reported the 151 K onset in Hg-1223 described above.^[15] See Claims of room-temperature superconductivity.

Computational search

For phonon-mediated superconductors T_c can be calculated from a proposed crystal structure: density functional theory gives the lattice vibrations and their coupling to the electrons, and Eliashberg theory gives T_c from these.^[17] One survey estimated T_c for about 200,000 metals that are stable or nearly stable against decomposition and found 541 above 10 K, among them LiMoN₂, predicted above 38 K.^[51] Hydrides predicted near 100 K at one atmosphere are in thermodynamically unfavorable phases, and among the thermodynamically stable cubic hydrides in one database the highest predicted T_c is 17 K.^[52] Four peer-reviewed reports describe superconductivity at 0.8 to 5.4 K in six compounds proposed with the help of machine-learning models, and two further searches found superconductivity at up to 9.7 K in samples that lacked the predicted structure or whose superconducting phase was not isolated.^{[53][54][55][56][57][58]} See Predicting superconductors.

Claims and retractions

Reports of superconductivity far above the accepted record have appeared since at least the 1970s, and none at room temperature has been confirmed.^[59] A 2020 paper in Nature from a laboratory at the University of Rochester reported 288 K at 267 GPa in a compound of carbon, sulfur and hydrogen and was retracted on 26 September 2022.^[9] A 2023 Nature paper from the same laboratory reported 294 K at 1 GPa (about 10,000 atmospheres) in lutetium hydride with a little nitrogen added. Another group found no superconductivity in the material, and the paper was retracted on 7 November 2023.^[60][10] A university investigation concluded that the head of the laboratory had committed research misconduct, including data fabrication.^[61][62] In July 2023 two preprints claimed superconductivity at 400 K or above at one atmosphere in LK-99, a copper-substituted lead apatite (a lead phosphate).^[63][64] Within weeks other laboratories traced the reported drop in resistance to a copper sulfide impurity and showed that pure crystals are insulators.^[11][65][66]

Uses

Superconductors in service today are cooled. Magnetic resonance imaging (MRI) magnets, the largest commercial use, are wound from niobium-titanium wire.^[67][68] The magnets of the Large Hadron Collider at CERN use the same alloy at 1.9 K, held there by 120 metric tons of helium and a cryogenic system that draws 40 megawatts of electricity.^[69] A superconductor that worked at room temperature would need no cryogenics, which would simplify such magnets and could make resistance-free power lines practical. Transmission and distribution losses in the United States averaged about 5% of electricity from 2018 through 2022.^[70]

For use at 300 K a conductor needs a high critical current and a high critical field, the largest current and magnetic field it can bear while superconducting, at that temperature. Current flows without loss only below a lower field, the irreversibility field, which falls to zero as the temperature approaches T_c.^[71] Conductors are therefore run well below T_c. A model coil for a fusion project reached 20.1 tesla with tape of rare-earth barium copper oxide (REBCO) at 20 K; YBa₂Cu₃O₇, the parent of that family, has a T_c of 93 K.^[72][45] Warren Pickett estimates that applications at room temperature would require a T_c of 375 to 400 K, and more for high current density.^[27]

See also

• Superconductivity
• History of superconductivity
• Superconducting materials
• High-pressure hydrides
• Claims of room-temperature superconductivity
• Verifying a superconductor
• Predicting superconductors
• Applications of superconductors
• Glossary

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