| perovskite | |
|---|---|
| Name | Perovskite |
| Caption | Crystal structure schematic of a perovskite ABO3 unit cell |
| Category | Oxide mineral / Crystal structure type |
| Formula | ABO3 (prototype: CaTiO3) |
| System | Cubic (ideal) |
| Symmetry | Pm3m (ideal) |
perovskite
Perovskite refers to a class of materials that share the same crystal structure as the mineral CaTiO3 and more broadly to the ABO3 structural motif. In the context of Quantum physics, perovskites are important because their lattice symmetry, electronic degrees of freedom, and strong coupling between charge, spin and lattice enable emergent quantum phenomena and tunable quasiparticles relevant to condensed matter physics and quantum device applications.
The perovskite structure is typified by a cubic network in which a larger A-site cation occupies the 12-coordinate cuboctahedral site, a smaller B-site cation sits at the octahedral center, and oxygen anions form corner-sharing BO6 octahedra. Structural deviations produce variants such as orthorhombic, tetragonal and rhombohedral perovskites via octahedral tilts and distortions described by Glazer notation. Classification schemes distinguish between oxide perovskites (e.g., SrTiO3, BaTiO3, CaTiO3), halide perovskites (e.g., methylammonium lead iodide MAPbI3), double perovskites (A2BB'O6 such as Sr2FeMoO6), and layered Ruddlesden–Popper phases (e.g., Sr2RuO4 family). Tolerance factor concepts (Goldschmidt tolerance factor) and ionic radii criteria determine stability ranges and propensity for structural phase transitions. Crystallographic defects, A-/B-site ordering, and heteroepitaxy produce symmetry breaking crucial to quantum behavior.
Electronic structure of perovskites is governed by B-site d-orbitals, A-site ionic potentials, and ligand (oxygen or halide) p-orbitals. Hybridization between transition-metal d states and anion p states yields bandwidth control and correlation strength, affecting Mott physics and band insulator–metal transitions. Band-structure calculations employing density functional theory (DFT) and beyond-DFT methods (e.g., DMFT, GW approximation) reveal narrow bands, flat-band features, and Rashba-type spin–orbit splitting in heavy-element halide perovskites (e.g., lead or tin compounds). Strong spin–orbit coupling in 5d perovskites (such as iridates like Sr2IrO4) leads to novel Jeff=1/2 states. Carrier effective masses, exciton binding energies, and polaron formation in hybrid perovskites impact quantum transport, optoelectronic response, and coherent quasiparticle lifetimes measured by ARPES and STM.
Perovskites host a broad spectrum of quantum orders. High-temperature superconductivity in copper oxide perovskite-derived cuprates (e.g., YBCO, La2-xSrxCuO4) provided paradigms for unconventional pairing and quantum criticality. Ruthenate perovskites such as Sr2RuO4 exhibit unconventional superconductivity with complex order parameters. Ferroelectricity in perovskites (for example, BaTiO3 and PbTiO3) couples soft phonon modes to polar order, enabling quantum paraelectric behavior observed in SrTiO3 near zero temperature where quantum fluctuations suppress long-range order. Magnetic perovskites, including manganites (La1-xCaxMnO3) and double perovskites, show colossal magnetoresistance, spin–charge separation, and emergent phenomena like spin spirals and skyrmion textures. Interplay between superconductivity, magnetism, and ferroelectricity enables multiferroic phases and proximity effects that are central to quantum materials research.
Engineered perovskite heterostructures, interfaces and superlattices (e.g., LaAlO3/SrTiO3 interface) create two-dimensional electron gases (2DEGs) with tunable carrier density, Rashba spin–orbit coupling, and superconductivity. Halide perovskites are prominent in photovoltaics and are investigated for their quantum light emission properties, single-photon sources, and spintronics. Oxide perovskites are platforms for oxide electronics, memristors, and quantum capacitors; companies and consortia such as Oxford Instruments and national labs (e.g., Argonne National Laboratory, Max Planck Society) support device development. Integration with superconducting qubits and hybrid quantum circuits explores coupling between collective modes (plasmons, phonons) and quantum two-level systems, aiming at sensors, transducers, and novel qubit materials.
Perovskite films and crystals are synthesized by solid-state reactions, molecular beam epitaxy (MBE), pulsed laser deposition (PLD), chemical vapor deposition (CVD), and solution processing for hybrid halide perovskites. Strain engineering via epitaxial growth on substrates (e.g., SrTiO3, LaAlO3) tunes octahedral rotations and electronic bandwidths. Chemical doping, oxygen vacancy control, and heterointerface design enable carrier density and correlation tuning. Nanostructures—quantum dots, nanowires, and two-dimensional perovskites—exhibit quantum confinement, enhanced exciton binding, and size-dependent spin–orbit effects exploited in optoelectronics and quantum emitters. Advanced characterization with transmission electron microscopy (TEM), X-ray diffraction (XRD), and ultrafast spectroscopy links synthesis parameters to emergent quantum properties.
Theoretical descriptions employ tight-binding Hamiltonians, Hubbard and t–J models for correlated electrons, and spin–orbit-coupled models for 4d/5d systems. First-principles DFT provides ground-state structures and band dispersions, often augmented by DMFT to capture strong correlations and temperature-dependent spectral functions. Model Hamiltonian studies, quantum Monte Carlo, and tensor network methods probe phase diagrams, topological phases, and superconducting instabilities. Multiscale approaches couple ab initio phonon calculations to electron–phonon coupling models to predict ferroelectric transitions and polaron dynamics. Collaborative efforts across universities and institutes (e.g., Harvard University, MIT, University of Cambridge) advance predictive design of perovskite quantum materials for application in next-generation quantum technologies.
Category:Perovskites Category:Quantum materials Category:Crystal structure types