The problem
An ordinary wire turns some electrical energy into heat as current flows. A superconductor can carry direct current without that resistance. Imagine keeping this property in an ordinary room, without deep cooling or a press squeezing the material.
That is the target here: reproducible superconductivity around 20–25°C at normal atmospheric pressure.[1] [5]
An ordinary wire heats up as current flows; a superconductor can carry direct current without that resistive loss. Can a reproducible material keep this property around 20–25°C at normal atmospheric pressure?
Superconductivity requires electron pairing and collective phase coherence: the pairs form a coordinated quantum state. Raising the critical temperature, Tc, therefore requires both suitable electronic interactions and a material structure that supports that state under the intended operating conditions.
The target is about 293–298 K at atmospheric pressure. The 2019 LaH10 experiment reported Tc near 250 K at about 170 GPa, supported by zero resistance, an isotope effect and magnetic-field dependence. The 2026 HgBa2Ca2Cu3O8+δ study reports an ambient-pressure resistive onset up to 151 K after pressure quenching. Onset marks the start of the transition; it is not the temperature at which resistance has necessarily reached zero.[1] [2] [3] [5]
Temperature and pressure
Superconductivity through time
Measurements and sources
Circle: resistive onset. Diamond: magnetic onset. Triangle: other reported transition. Square: reference value. These criteria are different ways to identify a transition; a reported onset is not automatically zero resistance.
The 151 K pressure-quench result is a resistive onset with limited retention. Pressure was used during preparation, then released. None of the plotted results establishes stable, reproducible superconductivity at room temperature and ambient pressure.
| Material and date | Temperature | Pressure | Criterion and source |
|---|---|---|---|
| Mercury1911 · historical experiment | 4.2 K · approximately | Ambient operation (1 atm plotting reference)Historical cryogenic resistance experiment; normal operating-pressure context, no exact sample pressure read | electrical resistance disappearance Macroscopic quantum phenomena from pairing in superconductors. Introduction, reproduced Onnes Fig. 17 as Fig. 1; indexed complete introductory passage indexed selected primary text and figure description; direct PDF open failed. 1911 is historical experiment year, not this lecture's publication year. Not a 1911 Meissner measurement. |
| LeadTypical reference value | 7.19 K · typical reference | Ambient operation (1 atm plotting reference)Official NBS cavity-material reference, uncompressed elemental material | typical bulk transition reference The role of superconductivity in the space program: an assessment of present capabilities and future potential. NBSIR 78-885; chapter VII Microwave applications, printed p. 119 (PDF p. 139), lines 3659–3661 full PDF text, selected chapter and report metadata. Reference temperatures, not dated discoveries or new measurements; surface cleanliness and strain matter. |
| NiobiumTypical reference value | 9.25 K · typical reference | Ambient operation (1 atm plotting reference)Official NBS cavity-material reference, uncompressed elemental material | typical bulk transition reference The role of superconductivity in the space program: an assessment of present capabilities and future potential. NBSIR 78-885; chapter VII Microwave applications, printed p. 119 (PDF p. 139), lines 3659–3661 full PDF text, selected chapter and report metadata. Reference temperatures, not dated discoveries or new measurements; surface cleanliness and strain matter. |
| Nb–Ge sputtered film1974 · paper publication | 23.2 K ± 0.2 K · reported onset | Ambient operation (1 atm plotting reference)Inference: accessed abstract describes sputtered films, with no continuing applied compression; pressure not numerically measured | transition onset measurement unspecifiedreported ± range; statistical meaning unspecified Superconductivity with onset above 23°K in Nb–Ge sputtered films. Complete publisher Abstract and publication metadata complete indexed publisher abstract; body not accessed. Abstract does not state which measurement determines onset. Ambient classification is an inference from unpressurized film experiment, not an exact pressure measurement. Do not date this 23.2 value to 1973. |
| Ba–La–Cu–O mixed-phase material1986 · historical experiment and original publication | 35 K · reported onset | Ambient operation (1 atm plotting reference)Author lecture distinguishes original 35 K transition from later hydrostatic-pressure enhancement | resistive onset Possible high Tc superconductivity in the Ba–La–Cu–O system. Complete Abstract and publisher publication month publisher abstract. Abstract alone does not establish an exact 35 K value or zero resistance at 35 K. Perovskite-type oxides—the new approach to high-Tc superconductivity. Printed p. 432, paragraph before Fig. 1.6; Fig. 1.5; p. 439 replication and pressure distinction indexed selected full primary passages; direct PDF open failed. Lecture describes later magnetic work and external confirmations separately; 35 K point is not recoded as magnetic onset or zero resistance. |
| Y–Ba–Cu–O mixed-phase material1987 · paper publication | 80–93 K; plotted at 93 K | Ambient operation (1 atm plotting reference)Ambient pressure stated in primary title and abstract | resistive and magnetic reported transition Superconductivity at 93 K in a new mixed-phase Y–Ba–Cu–O compound system at ambient pressure. Complete publisher Abstract and metadata publisher abstract. 93 K is upper end of reported interval, not formal measurement error or a proved zero-resistance threshold. Original material mixed-phase. |
| Hg–Ba–Ca–Cu–O mixed-phase/intergrowth1993 · paper publication | 133 K · approximately | Ambient operation (1 atm plotting reference)Ambient-pressure reference established in later primary hydride context; original abstract describes uncompressed multiphase material | magnetic and resistive reported transition Superconductivity above 130 K in the Hg–Ba–Ca–Cu–O system. Complete publisher Abstract; later primary hydride reports identify this as ambient-pressure context publisher abstract. Not a pure-phase, exact onset or zero-resistance claim. Ambient classification combines this report with later primary context. Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system. Author PDF p. 3 magnetic onset; Fig. 4 caption PDF pp. 11–12 pressure 155 GPa; pp. 2,4–5 preparation and electrical measurements final publisher abstract plus author preprint selected main text, methods and figure captions. Exact displayed 203 point is magnetic onset, not zero resistance at 203 K. 155 GPa and 203 K must be paired from Fig. 4. Author preprint methods are version-qualified. |
| HgBa2Ca2Cu3O8+δ1994 · paper publication | 164 K · approximately | About 31 GPa during operation | resistive onsetreported approximate pressure uncertainty, converted by 31×0.05 Superconductivity up to 164 K in HgBa2Ca(m−1)Cu(m)O(2m+2+δ) (m=1,2,3) under quasihydrostatic pressures. PDF p. 1 Abstract; p. 2 pressure and temperature calibration, onset definition and 31 GPa maximum full four-page primary PDF, selected methods/results. Nonzero resistance background and long tail are reported. Instrument uncertainty is not a formal uncertainty on rounded onset. |
| Magnesium diboride2001 · paper publication | 39 K · reported transition | Ambient operation (1 atm plotting reference)Uncompressed bulk experiment context; continuing compression not reported in accessed abstract | bulk superconductivity magnetic and resistive Superconductivity at 39 K in magnesium diboride. Complete indexed publisher Abstract indexed publisher abstract; direct open failed. Exact onset versus zero-resistance criterion not supplied by accessed abstract. No continuing compression reported in accessed material. |
| Sulfur hydride (H3S assignment)2015 · final paper publication | 203 K ± 1 K · magnetic onset | 155 GPa during operation | zero field cooled magnetic onsetsource reports 203(1) K; statistical meaning not restated Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system. Author PDF p. 3 magnetic onset; Fig. 4 caption PDF pp. 11–12 pressure 155 GPa; pp. 2,4–5 preparation and electrical measurements final publisher abstract plus author preprint selected main text, methods and figure captions. Exact displayed 203 point is magnetic onset, not zero resistance at 203 K. 155 GPa and 203 K must be paired from Fig. 4. Author preprint methods are version-qualified. |
| Lanthanum hydride LaH102019 · final paper publication, not 2018 preprint | 250 K · approximately | About 170 GPa during operation | reported resistive transition onset Superconductivity at 250 K in lanthanum hydride under high pressures. Final Abstract/metadata; author preprint PDF pp. 1–3 transition and maximum near 170 GPa; Fig. 1–2; Methods p. 7 final publisher abstract plus 2018-12-04 author preprint v1 selected results/methods. Multiple resistive transitions fall to zero, but 250 K is reported transition/onset, not necessarily completed zero resistance. Meissner measurement was not supplied by preprint. Do not substitute later near-room-temperature claims. |
| Pressure-quenched HgBa2Ca2Cu3O8+δ2026 · final paper online publication | 151 K · first warming onset | Ambient operation (1 atm plotting reference) Prepared at 18.9 GPa and quenched at 4.2 K; pressure was released before the plotted measurement.Pressure released; primary Experiment 5 warming curve 15 at ambient pressure | resistive onset dR dTlimited thermal/time retention; no room-temperature stable operation Ambient-pressure 151-K superconductivity in HgBa2Ca2Cu3O8+δ via pressure quench. Experiment 5, Fig. 2E curve 15 and Fig. 2F indexed relevant complete primary Results/Methods passages; direct PNAS/PMC blocked; SI not accessed. After quenching at 4.2 K, values are first warming curves. Companion cooling values 147/148/150 K. Limited stability; retrieved magnetic onset about 140 K is a different state; unrepeated 172 K excluded. |
Scope
Reproducible superconductivity around 20–25°C at normal atmospheric pressure, with synthesis conditions distinguished from operating conditions.
What remains open
Some experiments reach much warmer temperatures while keeping tiny samples under enormous pressure. Others retain an improved superconducting state after pressure is released, but still need deep cooling.
The challenge is to achieve both ordinary temperature and ordinary pressure in the same material, with results that other laboratories can reproduce.[1] [2] [3]
In the cuprate experiment, low-temperature pressure release retained enhanced transitions, but warming, storage and retrieval could lower them. Magnetic measurements on a retrieved sample supported bulk superconductivity with a transition around 140 K; that is distinct from the 151 K resistive onset measured after quenching. The mechanism that stabilizes the retained state still needs clarification.
A candidate for the joint target needs reproducible synthesis, phase identification and consistent electrical and magnetic evidence at the stated temperature and pressure. Theory must address whether the predicted structure can be made and persist, alongside pairing and coherence. The retracted lutetium-hydride claim provides no evidence of success.[1] [3] [4]
Why it matters
A superconducting MRI magnet relies on cooling to stay superconducting. A material that worked in an ordinary room could reduce that refrigeration burden and make other superconducting devices easier to use.
It would still need to carry useful currents, withstand magnetic fields and be made into dependable components. The benefits depend on those properties too.[1] [5]
Separating synthesis conditions from operating conditions opens a useful possibility: an expensive preparation step might produce a state that later works without compression. Understanding why a metastable state survives—or relaxes into another phase—would help connect material predictions with workable preparation routes.
Practical value also depends on the usable current density and magnetic-field range at the operating temperature, as well as lifetime and fabrication into wires, films or other components. Room-temperature superconductivity could reduce cooling demands; the transition temperature alone cannot establish how much a device would benefit.[1] [3] [5]
Research directions
2 directions to explore
Ambient-pressure phase stability
Find compositions and preparation routes that preserve a promising superconducting phase when pressure is removed. Metastability can provide a route, but retained properties may change with temperature and time.
Materials and pairing mechanisms
Identify structures and interactions that support a high transition temperature under the desired pressure conditions. Predicting a favorable electronic structure must be connected to synthesizing and characterizing the intended material.
Sources
Partial results
Demonstrates superconductivity in lanthanum hydride near 250 K at about 170 GPa. Scope: Small samples held at extreme pressure in a diamond anvil cell.
The temperature is below ordinary room temperature, and the experiment does not establish superconductivity at ambient pressure.
Source date: 2019-05-22Published primary experimental researchRead the source ↗Reports an ambient-pressure superconducting transition onset up to 151 K in a pressure-quenched mercury-based cuprate. Scope: A metastable state prepared through high-pressure treatment and rapid pressure release at low temperature.
151 K is an onset temperature and remains far below room temperature. The authors report limited thermal and temporal stability; warming and handling can reduce the retained transition temperature.
Source date: 2026-03-09Published primary experimental researchRead the source ↗- The path to room-temperature superconductivity: A programmatic approach
Notes on The path to room-temperature superconductivity: A programmatic approach
A PNAS research perspective on materials discovery, metastability, synthesis and characterization. It proposes research routes, rather than demonstrating room-temperature superconductivity at ambient pressure.
- Superconductivity at 250 K in lanthanum hydride under high pressures
Notes on Superconductivity at 250 K in lanthanum hydride under high pressures
Primary experimental evidence for superconductivity in LaH10 near 250 K and 170 GPa, including zero resistance, isotope effects and magnetic-field dependence. Pressure is essential to its scope.
- Ambient-pressure 151-K superconductivity in HgBa2Ca2Cu3O8+δ via pressure quench
Notes on Ambient-pressure 151-K superconductivity in HgBa2Ca2Cu3O8+δ via pressure quench
A primary PNAS study reporting a resistive transition onset up to 151 K at ambient pressure after pressure quenching. The metastable phase has limited thermal and temporal stability.
- Retraction Note: Evidence of near-ambient superconductivity in a N-doped lutetium hydride
Notes on Retraction Note: Evidence of near-ambient superconductivity in a N-doped lutetium hydride
The publisher's retraction notice identifies material-provenance, measurement and data-processing concerns. The withdrawn claim is not evidence that the ambient-pressure target has been achieved.
- DOE Explains...Superconductivity
Notes on DOE Explains...Superconductivity
Official explanation of resistance, superconducting currents and magnetic fields, cooling requirements, critical current, and applications including MRI magnets. This basic explainer does not establish the room-temperature ambient-pressure target.