| REBCO | |
|---|---|
| Name | REBCO |
| Formula | REBa2Cu3O7−δ |
| Discovery | 1987 (YBa2Cu3O7) |
| Group | High-temperature cuprate superconductors |
| Critical temperature | Up to ~93 K (for YBCO) |
| Crystal system | Orthorhombic / Perovskite-derived |
| Applications | Power devices, magnets, quantum devices |
REBCO
REBCO is a family of high-temperature superconducting cuprates with nominal formula REBa2Cu3O7−δ, where RE denotes a rare-earth element such as Yttrium or Gadolinium. REBCO compounds are notable in the context of Quantum physics because they combine layered copper-oxide electronic structure, relatively high critical temperature (Tc) and strong anisotropic quantum coherence that enable studies of unconventional pairing, vortex quantum dynamics and potential incorporation into quantum devices and sensors.
REBCO refers to the class of rare-earth barium copper oxide superconductors derived from the prototype YBa2Cu3O7−δ (commonly called YBCO). Substituting different rare-earth ions (RE = Yttrium, Neodymium, Samarium, Europium, Gadolinium, etc.) produces chemically similar phases with variations in lattice parameters and pinning behavior. These materials belong to the family of high-Tc superconductors discovered in the late 1980s and are characterized by layered perovskite-derived structures, strong electron correlations and a superconducting transition that can exceed liquid-nitrogen temperatures, facilitating experiments related to quantum coherence and macroscopic quantum phenomena.
The REBCO structure is an orthorhombic distortion of a perovskite-derived unit cell comprised of CuO2 planes, Cu–O chains, RE layers and BaO layers. The CuO2 planes are primarily responsible for the low-energy electronic states and superconductivity; the charge reservoir layers control hole doping via oxygen stoichiometry (δ). Electronic structure probes such as ARPES and STM have revealed strong anisotropy, Fermi surface reconstruction and pseudogap behavior familiar from studies at Stanford and Max Planck–affiliated laboratories. The combination of quasi-two-dimensional dispersion, strong Coulomb repulsion and proximity to antiferromagnetism produces correlated electronic phases and rich phase diagrams relevant to theoretical work by groups around Princeton, Cambridge and MIT.
REBCO cuprates exhibit unconventional superconductivity commonly described by a predominantly d-wave pairing symmetry (dx2−y2), supported by phase-sensitive experiments by researchers at UIUC and UC Berkeley. The pairing mechanism is widely attributed to electronic correlations and spin fluctuations in the CuO2 planes rather than conventional electron–phonon coupling described by BCS theory. Theoretical models developed at institutions such as Columbia University and Rutgers University emphasize antiferromagnetic exchange (J) and Hubbard/ t–J models to capture pairing and competing orders, including charge-density waves and the pseudogap regime that affect superconducting coherence lengths and quasiparticle spectra.
In applied magnetic fields REBCO enters a mixed (vortex) state where quantized flux lines (Abrikosov vortices) thread the superconductor. The vortex core physics, vortex lattice melting, and quantum creep are critical to both fundamental quantum studies and device robustness. Pinning landscapes produced by defects, nanoparticle inclusions and columnar defects (often engineered at places like ORNL and LANL) determine critical current density (Jc). Quantum tunneling of vortices, quantum vortex glass states and phase-slip centers are active topics linking REBCO behavior to macroscopic quantum tunneling and dissipative quantum dynamics studied in low-temperature physics laboratories worldwide.
REBCO fabrication includes bulk synthesis, melt-textured growth, metal–organic chemical vapor deposition (MOCVD), pulsed laser deposition (PLD), and metal-organic deposition (MOD) on buffered substrates for coated conductors. Thin-film growth on single-crystal substrates (e.g., SrTiO3, LaAlO3, MgO) enables epitaxial films used in quantum device prototyping. Industrial-scale coated-conductor architectures employing IBAD or RABiTS textured templates are developed by companies and research centers such as SuperPower and AMSC to optimize in-field Jc and mechanical properties. Growth control of oxygen stoichiometry, grain boundary engineering and nanoscale pinning inclusions are central to achieving superconducting properties relevant for quantum sensors and circuits.
REBCO has been explored for quantum technologies including superconducting quantum interference devices (SQUIDs), single-photon detectors, and hybrid qubit architectures. High-Tc SQUIDs enable operation at elevated temperatures and have been demonstrated in biomagnetic sensing and geophysics by groups at University of Cambridge and Harvard University. Hybrid approaches investigate coupling REBCO resonators to spin ensembles and nanomagnets for quantum memory and transduction; centers such as NIST and CEA Saclay have investigated high-Q microwave resonators and nonlinear devices. Challenges remain for implementing REBCO as a platform for conventional superconducting qubits (e.g., transmon) due to short coherence times, granularity and dissipation linked to nodal quasiparticles, although proposals exist for exploiting d-wave symmetry and Andreev bound states in novel qubit designs.
Key limitations for quantum applications include grain-boundary weak links, anisotropic gap nodes that host low-energy quasiparticles, and material heterogeneity that reduces coherence times and increases loss in resonators. Ongoing research at academic and government labs (e.g., University of Twente, ETH Zurich, Argonne National Laboratory) focuses on improved epitaxy, engineered pinning arrays, interface control, and hybrid device integration with low-loss dielectrics. Theoretical and experimental efforts continue to probe the interplay between strong correlations, disorder and superconducting phase coherence, with goals of mitigating dissipation for quantum sensing, exploring novel d-wave qubits and leveraging REBCO’s high Tc for cryogenic-electronics integration.
Category:High-temperature superconductors Category:Cuprate superconductors