Reference › Claims of room-temperature superconductivity

Claims of room-temperature superconductivity

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

Claims of room-temperature superconductivity are reports that a material superconducts, carrying electric current with zero resistance and expelling magnetic fields, at or near room temperature, about 293 to 300 kelvin (K), or 20 to 27 °C. Such reports have been made since the 1970s.^[9] None has been reproduced by an independent laboratory. The highest transition temperature (T_c), the temperature below which a material superconducts, that more than one group has confirmed is about 250 K (−23 °C), in lanthanum hydride held at about 170 gigapascals (GPa), about 1.7 million atmospheres.^[1][2] This article also covers unconfirmed reports of superconductivity far above the record of their time, the latest made in 2026.

Signals reported in the 1970s and 1980s faded or were never confirmed.^[10][9] Three papers published between 2020 and 2023 by one group at the University of Rochester, each reporting a transition above 260 K, were retracted, and a university investigation concluded that the group leader had fabricated data.^[11] The signals of LK-99, announced in July 2023, were explained within four weeks: its fall in resistivity came from a copper sulfide impurity and its partial levitation from weak ferromagnetism.^[6][12] A 2025 preprint, a paper not yet peer reviewed, reports that the resistance of a lanthanum scandium hydride at 260 GPa begins to fall at up to 298 K. It has not been reproduced.^[7][8]

Unidentified superconducting objects

Reports of superconductivity near room temperature appeared throughout the 1970s and 1980s and became more frequent after the cuprate superconductors were discovered in 1986.^[9] Physicists call such reports unidentified superconducting objects, or USOs.^[13][9] A 2020 review applies the label to results that have not been reproduced or that lack data on magnetic susceptibility, the response of a material to an applied magnetic field.^[9] One of its examples is a 1974 report of a current in aluminum-carbon-aluminum sandwiches at room temperature that the author took as a sign of superconductivity and that has not been confirmed.^[9][14]

Other signals of the period were below room temperature but far above the record of the time, about 23 K.^[15] In 1978 copper chloride (CuCl) under about 0.5 GPa (about 5,000 atmospheres) was reported to become an almost ideal diamagnet, opposing an applied magnetic field almost as completely as a superconductor, below about 170 K while its temperature was swept at about 20 K per minute. After several cycles of cooling and warming, the temperature below which the effect appeared had fallen about threefold.^[10] In 1980 superconductor-like behavior was reported well above 77 K, the boiling point of liquid nitrogen, in cadmium sulfide that had been compressed to more than 4 GPa and released at more than 100 GPa per second. The signal decayed with time.^[10]

In 1989 an apparent zero-resistance state below about 300 K was reported in films of oxidized polypropylene.^[10][9] In July 2018 a preprint reported that films of silver particles in a gold matrix lost measurable resistance at ambient pressure below 236 K and became strongly diamagnetic; a 2019 revision gave up to 286 K.^[16] Sixteen days after the first version a comment showed that two susceptibility curves presented as separate measurements carried the same pattern of noise, and the 2020 review lists the result as a possible USO.^[17][9]

Hydride claims from the University of Rochester

By 2019 two hydrogen-rich compounds, or hydrides, had been reported to superconduct under pressure, and other groups later measured the same transitions: the sulfur hydride H₃S at 203 K and 155 GPa, and lanthanum hydride (LaH₁₀) at about 250 K and about 170 GPa (see High-pressure hydrides).^{[18][1][19][2]} In 2018 one group reported resistance drops in lanthanum hydride beginning near 260 K at 190 GPa, and as high as 280 K in two further samples, above the roughly 250 K that other groups reproduced.^[20][1][2]

Between 2020 and 2023 a group led by Ranga Dias at the University of Rochester reported three higher values.^[21][22][23] All three papers have been retracted.^[3][5][4]

Carbonaceous sulfur hydride

On 14 October 2020 the journal Nature published the group's report of superconductivity at 287.7 K (about 15 °C) in a compound of carbon, sulfur and hydrogen compressed to 267 GPa in a diamond anvil cell, which squeezes a microscopic sample between the tips of two diamonds.^[21] The evidence listed was zero resistance, a magnetic susceptibility signal measured up to 190 GPa, and a transition that moved to lower temperature in magnetic fields of up to 9 tesla (T), as a superconducting transition does.^[21]

Nature attached an editor's note on 30 August 2021 about undeclared restrictions on access to the data. In November 2021 Dias and a coauthor posted what they described as the raw susceptibility data, and on 15 February 2022 Nature added a note about how the data had been processed.^[21][24] A diamond anvil cell has about 100 million times the mass of its sample and contributes a background signal to magnetic measurements.^[19] An analysis first posted in January 2022 and revised through August 2022 concluded that the curves labeled as measured voltage matched the result of adding a noisy background to the published susceptibility signal, the reverse of the subtraction the paper described.^[25] Nature retracted the paper on 26 September 2022. The retraction note states that the background subtraction applied to the susceptibility data used a non-standard, user-defined procedure that the paper had not described, and that all nine authors disagreed with the decision.^[3] A study posted the following month extracted the resistance curves from the published figure files, because the raw files had not been released, and found that over one temperature interval they consisted of at least two signals of different digital precision.^[26] Mikhail Eremets of the Max Planck Institute for Chemistry said in 2023 that other researchers, his own group among them, had been unable to reproduce the result.^[27]

Papers in Physical Review Letters

In 2021 the group reported in Physical Review Letters a transition at 262 K (−11 °C) at 182 GPa in an yttrium superhydride, a hydride with an unusually high hydrogen content.^[22] On 15 August 2023 the journal retracted a different 2021 paper with Dias among its authors, on the electrical resistance of manganese disulfide, after four independent experts raised serious doubts about the origin of three of its low-temperature resistance curves.^[28][29] It retracted the yttrium paper on 13 June 2024.^[5] Another group published a measurement of 243 K in the yttrium hydride YH₉ at 201 GPa in 2021.^[30]

Nitrogen-doped lutetium hydride

On 8 March 2023 Nature published the group's report of a T_c of up to 294 K (21 °C) in lutetium hydride with a little nitrogen added (nitrogen-doped), at 10 kilobar (1 GPa, about 10,000 atmospheres).^[23] A week later a group at Nanjing University posted results on samples with the same crystal structure; the version published in Nature reports no superconductivity down to 2 K between 0.4 and 40.1 GPa.^[31] One preprint reported resistance data in agreement with the claim, measured on material prepared by the Rochester group.^[32][29] Nature added an editor's note on 1 September 2023 saying that the reliability of the data was in question, and retracted the paper on 7 November 2023 at the request of eight of its eleven authors. They stated that the paper did not accurately reflect the provenance of the materials, the measurements made, or the data processing. The note adds that the journal found concerns about the resistance data credible and unresolved, and that Dias and two other authors had not stated whether they agreed.^[23][4]

University investigation

Three inquiries by the University of Rochester, two completed in May 2022 and a third after the September 2022 retraction, reported no evidence of misconduct, and in August 2023 the university announced a new investigation.^[29] Dias said in 2023 that there had been no data fabrication or data manipulation in his group's work.^[27] The confidential 124-page report of the investigation, disclosed in a lawsuit and described by Nature in April 2024, concluded that Dias had committed data fabrication, falsification and plagiarism.^[11] On 12 June 2024 the 2021 posting of raw susceptibility data was withdrawn, with a note quoting the investigation: the data presented as measured had most probably been computed from the published data.^[24] On 19 November 2024 Nature reported the university's confirmation that it no longer employed Dias.^[33]

LK-99

On 22 July 2023 a group in South Korea posted two preprints on a material it called LK-99, a lead phosphate of the apatite family in which copper replaces part of the lead, with the formula Pb_10−xCu_x(PO₄)₆O and x between 0.9 and 1.1.^[34][6] The preprints reported superconductivity at ambient pressure up to at least 400 K (127 °C).^[35] As evidence they listed zero resistivity, a critical current, a critical magnetic field and the Meissner effect, the expulsion of a magnetic field from a superconductor, and they described a sample levitating over a magnet.^[35][34]

LK-99 is made by solid-state synthesis, the heating of mixed powders.^[34] Other laboratories made it and posted results within three weeks:

• 31 July: a group at India's National Physical Laboratory made the material by the published route and saw no levitation or diamagnetism at room temperature.^[36]
• 6 August: a group at Peking University found that its samples consisted mainly of the lead phosphate and copper sulfide (Cu₂S). Small flakes half levitated over a magnet, which the group attributed to weak ferromagnetism and the shape of the flakes. It saw no Meissner effect and no zero resistance.^[12][6]
• 8 August: a group at the Chinese Academy of Sciences measured a structural phase transition of Cu₂S near 385 K (112 °C), at which the resistivity falls sharply without reaching zero.^[37][6]
• 11 August: a group at the Max Planck Institute for Solid State Research in Stuttgart reported single crystals of the pure compound, without copper sulfide. They were transparent and highly insulating, and showed no sign of superconductivity between 2 and 800 K.^[38][6]

Cu₂S has a known phase transition at 104 °C (377 K), within one degree of the 104.8 °C at which the original authors had reported a tenfold fall in resistivity, from about 0.02 to about 0.002 ohm centimeters.^[39][6] The measured transition temperature differs between warming and cooling.^[37] On 16 August 2023, 25 days after the preprints, Nature reported that after dozens of replication efforts many specialists regarded the question as settled: LK-99 is not a room-temperature superconductor, and impurities, chiefly Cu₂S, account for the fall in resistivity.^[6]

Lanthanum scandium hydride

On 29 September 2025 a group at Jilin University posted a preprint reporting superconductivity with onset temperatures, at which the resistance begins to fall, of 271 to 298 K between 195 and 266 GPa in a lanthanum scandium hydride (for the compound and its prediction, see High-pressure hydrides).^[7] The authors identified it as LaSc₂H₂₄ by X-ray diffraction, which locates the metal atoms but not the hydrogen.^[7][40] The highest onset, 298 K (25 °C), was measured at 260 GPa.^[7] Of five diamond anvil cells, four gave resistance data. Two of the four showed zero resistance, and in one of them the transition fell from 296 K to 285 K in a magnetic field of 9 T.^[7] The preprint contains no measurement of magnetization or susceptibility, which the authors attribute to samples 10 to 20 micrometers across, and no test with deuterium in place of hydrogen, which would show the isotope effect seen in the reproduced hydrides.^[7][18][1] A specialist outside the group told Physics World that the resistance data strongly suggest superconductivity and that the diffraction leaves doubt about which structure is responsible.^[40]

A second group posted a preprint on 28 May 2026 on failed attempts to make the compound from an alloy of lanthanum and scandium at 250 to 280 GPa; a revision of 20 August 2026 added three, for seven in all. Four cells gave resistance data, none showing superconductivity between 245 and 300 K. No cell was shown by X-ray diffraction to contain LaSc₂H₂₄, so the attempts did not test whether the compound superconducts. The group suggested that the two metals may need to be deposited together when the alloy is prepared.^[8] As of October 2026 the original report remained a preprint without a journal reference and had not been reproduced.^[7][8]

Claimed records below room temperature

The highest T_c of a stable material at ambient pressure is found in the mercury cuprates: 133 K in HgBa₂Ca₂Cu₃O_8+δ (Hg-1223), reported in 1993, and 138 K in a 1995 sample in which thallium replaced part of the mercury.^[41][42] In March 2026 a group led from the University of Houston reported that crystals of Hg-1223, compressed to between 10 and 30 GPa and released from pressure at 4.2 K, a procedure called a pressure quench, kept a resistive onset of up to 151 K (−122 °C) at ambient pressure.^[43] The paper reports no zero resistance in this state, and a sample recovered from the pressure cell gave about 140 K by magnetization.^[43] The retained state lasted at least three days at 77 K, and its T_c degraded when it was heated above 200 K.^[43]

In June 2026 a group at North Carolina State University reported ambient-pressure transitions at 112 K and 164 K in two phases of boron-doped Q-carbon, made by melting layers of boron and carbon with nanosecond laser pulses and cooling them rapidly, and at 120 K and 187 K in nanostructured samples.^[44] By October 2026 no group independent of the original authors had reported either effect.

List of claims

Recurring weaknesses

Three weaknesses recur among the claims made since 2018, and each corresponds to a check described in Verifying a superconductor.

In four cases the magnetic evidence was missing or did not hold up: the carbonaceous sulfur hydride paper was retracted over an undescribed background subtraction in its susceptibility data,^[3] the two susceptibility curves for silver in gold repeated the same noise,^[17] the levitation of LK-99 flakes was ferromagnetic,^[12] and the LaSc₂H₂₄ preprint reports no magnetization or susceptibility data.^[7]

Independent tests of the retracted and refuted claims did not reproduce them: attempts on the carbonaceous sulfur hydride transition were reported to have failed,^[27] tests of lutetium hydride and of LK-99 found no superconductivity,^[31][36][38] and the one report that supported the lutetium hydride claim used material from the original group.^[29]

The carbonaceous sulfur hydride data carried undeclared access restrictions, the susceptibility data posted as raw in 2021 were later withdrawn, and the raw resistance files had not been released a month after the retraction.^[21][24][26] The LaSc₂H₂₄ preprint offers further data on request.^[7] In a comment published in December 2024, fifteen physicists defending the reproduced hydride results asked that data in the field be made public.^[19]

Reports of zero resistance appeared in failed claims as well as accepted ones: the carbonaceous sulfur hydride, yttrium superhydride and LK-99 reports listed zero resistance or zero resistivity as evidence, and the silver-gold preprint reported a resistance below the resolution of its measurement.^{[21][22][35][16]}

See also

• Verifying a superconductor
• High-pressure hydrides
• History of superconductivity
• Room-temperature superconductor

References

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