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What have nickelate superconductors shown?

Nature reports superconductivity in an infinite-layer nickelate film and superconducting signatures in a different bilayer nickelate under pressure [1][2]. Later Nature papers report ambient-pressure film transitions, with important distinctions between onset, zero resistance, and magnetic response [3][4].

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A nickel oxide inspired by cuprates

Nature published Danfeng Li and colleagues' observation of superconductivity in an infinite-layer nickelate in 2019 [1]. In Nature, the team reported making strontium-substituted neodymium nickelate, Nd0.8Sr0.2NiO2, as a single-crystal thin film by chemically reducing a perovskite precursor [1]. The Nature team measured resistance, critical current density, and response to magnetic fields, reporting a superconducting transition from roughly 15 to 9 kelvin [1]. Their undoped NdNiO2 film instead showed a low-temperature resistance upturn, according to Nature [1]. The Nature comparison demonstrates why a material's exact composition matters when describing a reported transition [1].

Nature describes the infinite-layer nickelate as having the same crystal structure as an infinite-layer copper oxide, or cuprate [1]. The Nature papers explain that this structural resemblance motivated the search, but the materials contain different transition metals and should not be treated as electronically identical [1][2]. In the Nature paper, infinite-layer names a crystal structure, rather than an infinitely thick film or an unlimited stack manufactured in a laboratory [1]. Nature's 2019 result concerns a specifically prepared thin film, so its temperature range should not be transferred automatically to other nickelates, sample forms, or preparation routes [1].

A separate bilayer responds to pressure

In 2023, Sun and colleagues reported in Nature superconducting signatures near 80 kelvin in single crystals of La3Ni2O7 under high pressure [2]. Their Nature paper combined electrical resistance and mutual-inductance magnetic susceptibility measurements over a reported pressure range of 14.0 to 43.5 gigapascals [2]. Nature identifies this compound as a bilayer nickelate structure, distinct from the infinite-layer film in the 2019 study [1][2]. The near-80-kelvin figure in Nature therefore belongs to a pressurized crystal experiment, not to Li's ambient-pressure film [1][2].

Nature reported that the high-pressure phase had a different crystal arrangement and that the authors' calculations implicated nickel and oxygen orbitals, including orbitals connecting the two layers [2]. Those Nature calculations suggest a connection between structure and electronic behavior; they do not by themselves establish the superconducting pairing mechanism [2]. Nature's later discussion of the field also identified low superconducting volume fractions and competing structural phases as challenges in early pressurized samples [5]. As the Nature discussion illustrates, a resistance transition can reveal a conducting path without establishing that the entire specimen has entered the same state [5].

Pressure evidence extends to a substituted bulk sample

In 2024, Wang and colleagues reported in Nature on polycrystalline La2PrNi2O7, in which praseodymium replaces some of the lanthanum [5]. The Nature authors reported that substitution reduced intergrowth of competing phases and produced a nearly pure bilayer structure in their samples [5]. At 18 to 20 gigapascals, Nature reported an onset of 82.5 kelvin and zero resistance at 60 kelvin [5]. The Nature paper reported diamagnetic signals below about 75 kelvin above 15 gigapascals, supporting its interpretation of bulk superconductivity in that pressurized composition [5].

The Nature measurements also show why one temperature alone cannot summarize a whole experiment [5]. An onset marks the start of a transition in the Nature measurement, while zero resistance describes a lower-temperature endpoint in this particular sample [5]. The magnetic signal in Nature supplies a complementary observation about the superconducting response, rather than another name for the onset [5]. The Nature results improve the evidence for the substituted bilayer under pressure, but do not demonstrate the same temperatures in an unpressurized sample of the original La3Ni2O7 composition [2][5].

Strained films work without a pressure cell

Ko and colleagues reported in Nature in December 2024 that La3Ni2O7 thin films showed superconducting signatures at ambient pressure when grown under compressive epitaxial strain [3]. In these Nature films, the supporting substrate constrains the film's in-plane crystal dimensions, providing a different experimental condition from external pressure on a bulk crystal [3]. Nature reported onset temperatures of roughly 26 to 42 kelvin, with higher onsets associated with smaller in-plane lattice constants [3]. The zero-resistance temperature reported in Nature was much lower, around 2 kelvin [3].

Nature reported coexistence of other layered phases in the films and changes in transport after ozone annealing [3]. The Nature authors suggested that stacking defects, grain boundaries, and oxygen content could account for the low zero-resistance temperature, rather than establishing a single definitive cause [3]. A 2026 Nature author correction fixed resistivity-axis units and a temperature-axis label in several figures; the corrected paper retains the reported onset and zero-resistance temperatures [3][7]. These distinctions matter because the Nature onset cannot be quoted as the temperature at which Ko's film reached zero resistance [3].

Praseodymium films add magnetic evidence

In 2025, Zhou and colleagues reported in Nature on a different ambient-pressure film, La2.85Pr0.15Ni2O7, grown on a SrLaAlO4 substrate [4]. Nature described the three-unit-cell-thick film as a pure-phase single crystal under about 2% in-plane compressive strain relative to the bulk [4]. Nature reported a resistance onset of 45 kelvin, inferred from resistivity and magnetic-field response [4]. The transition toward zero resistance reported in Nature was consistent with a Berezinskii-Kosterlitz-Thouless-like transition at 9 kelvin [4].

Nature also reported a Meissner diamagnetic response measured by mutual inductance at 8 kelvin in Zhou's film [4]. That Nature magnetic observation is additional evidence for superconductivity, but it should not be moved up to the 45-kelvin onset [4]. The Nature authors described a transition over a substantial temperature interval, so the onset, the 9-kelvin transition analysis, and the 8-kelvin magnetic measurement answer different questions [4]. The film also differs in composition, substrate conditions, and thickness from the pressurized crystals and Ko's films described in Nature, making simple temperature rankings incomplete [2][3][4].

Oxygen, structure, and the road ahead

Dong and colleagues used electron imaging and spectroscopy to examine oxygen vacancies in La3Ni2O7, reporting their findings in Nature in 2024 [6]. In their sample, Nature reported that vacancies appeared primarily at inner apical oxygen sites between nickel layers, and oxygen content varied at the nanoscale [6]. Nature reported that the electronic structure also varied with the measured oxygen content [6]. Together with Ko's Nature observation of transport changes after ozone annealing, this result makes oxygen control an experimentally grounded concern when comparing specimens [3][6].

Nature's papers show a family of results across different structures, compositions, pressures, and film strains, rather than a single nickelate operating point [1][2][3][4][5]. They also leave a scientific question: Dong's Nature study identifies the relevant orbitals and the role of atomic deficiencies as unresolved parts of the pairing problem [6]. Researchers can compare the structural, electrical, and magnetic measurements in Nature while keeping the conditions attached to each number [2][4][5][6]. None of these particular Nature experiments establishes a room-temperature nickelate conductor or demonstrates a practical wire; their results concern cold laboratory samples under the stated conditions [1][2][3][4][5].

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