High-Temperature Superconductivity in Correlated Electron Systems

High-temperature superconductivity arises in materials where strong electron–electron interactions give rise to collective quantum states distinct from conventional metallic behaviour. In correlated electron systems such as cuprates and nickelates, electrons on transition-metal d orbitals experience Coulomb repulsion comparable to their kinetic energy. This balance fosters a rich phase diagram in which superconductivity emerges alongside or competes with charge, spin and orbital orders. The archetypal cuprate superconductors display d-wave pairing with transition temperatures exceeding 100 K, while recently discovered infinite-layer nickelates have triggered fresh investigation of how rare-earth spacer layers and orbital hybridisation influence pairing. Progress in thin-film synthesis, resonant spectroscopies and advanced numerical methods has deepened our understanding of the interplay between Mott physics, charge density waves and unconventional pairing. These insights carry global significance for applications in power transmission, magnetic resonance imaging and quantum information, motivating continued exploration of materials with higher critical temperatures and more robust superconducting phases.

Research from Nature Portfolio

Recent studies have probed the role of charge order and orbital hybridisation in infinite-layer nickelates. High-resolution X-ray scattering on fully reduced NdNiO₂ specimens has shown that earlier reports of commensurate 3a₀ charge density wave order originate from impurity phases rather than intrinsic nickelate behaviour, highlighting a key distinction from cuprates in which charge order is intertwined with superconductivity. This absence of static charge modulation refines the phase diagram of nickelate superconductors and refocuses attention on electronic correlations in the NiO₂ planes. Complementary first-principles calculations reveal a substantially stronger hybridisation between Ni dₓ²₋ᵧ² orbitals and itinerant interstitial-s electrons than previously thought, rather than with rare-earth d states. This hybridisation screens the Ni local moment, elevates the critical Coulomb interaction needed for magnetic order and alters the effective bandwidth. Together, these findings recalibrate theoretical models for pairing mechanisms in nickelates and emphasise the importance of subtle orbital mixing in correlated electron superconductors.

High-Temperature Superconductivity in Correlated Electron Systems publication trend

The graph below shows the total number of articles in high-temperature superconductivity in correlated electron systems across all publications each year (not limited to Nature Index journals).

Technical terms

High-temperature superconductivity: A quantum state in which electrical resistance vanishes and magnetic fields are expelled at transition temperatures well above those of conventional superconductors.

Correlated electron systems: Materials in which strong Coulomb interactions among electrons dominate their behaviour, often leading to magnetism, charge order and unconventional superconductivity.

Infinite-layer nickelates: A family of superconducting compounds with the formula RNiO₂ (R = rare earth) featuring NiO₂ planes analogous to CuO₂ planes in cuprates.

Charge density wave (CDW): A periodic modulation of electronic charge in a crystal, often coexisting with or competing against superconductivity.

Hybridisation: Mixing of electronic orbitals from different atoms or sublattices, which alters bandwidths, correlation strengths and magnetic properties.

Hubbard model: A minimal theoretical framework describing electrons on a lattice with on-site Coulomb repulsion and nearest-neighbour hopping, widely used to study correlated phenomena.

d-wave pairing: A superconducting order parameter with lobes of opposite sign, characteristic of many unconventional superconductors such as cuprates.

References

1. Absence of 3a0 charge density wave order in the infinite-layer nickelate NdNiO2. Nature Materials (2024).
2. A substantial hybridization between correlated Ni-d orbital and itinerant electrons in infinite-layer nickelates. Communications Physics (2020).
3. Similarities and Differences between LaNiO2 and CaCuO2 and Implications for Superconductivity. Physical Review X (2020).
4. Model Construction and a Possibility of Cupratelike Pairing in a New d9 Nickelate Superconductor (Nd,Sr)NiO2. Physical Review Letters (2020).
5. Solutions of the Two-Dimensional Hubbard Model: Benchmarks and Results from a Wide Range of Numerical Algorithms. Physical Review X (2015).