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An Unsettling Similarity Between Superconducting Iridates and Cuprates

By studying the iridates, a family of materials with strongly correlated electrons, researchers from IRAMIS unexpectedly highlighted a profound analogy between these compounds and high-temperature cuprate superconductors (YBaCuO). Besides their very promising potential, notably in spintronics, these materials could provide valuable clues to understand, at last, the origin of unconventional superconductivity in cuprates.
Published on 24 July 2017

Iridates such as Sr2IrO4 and La2CuO4 are lamellar materials whose properties may be adjusted by rhodium doping. In certain conditions and at low temperature, conduction electrons remain localized on their atom instead of "jumping" to the neighboring atom. The material then becomes a "Mott Insulator". This transition, as well as others (superconducting state or "spin liquid"), results from different electronic processes, classical and quantum, including electrostatic repulsion, the Pauli exclusion principle, and the relativist interaction between the speed of an electron and its spin (spin-orbit coupling). These materials, known for having strongly correlated electrons, offer many perspectives for spintronics, magnetic captors and high temperature superconductors.

Thanks to neutron scattering analyses and optical measurements, the scientists have discovered a new magnetic state found in several iridates. Under a proposed model for high critical temperature superconductors, this state would be generated by current loops comparable in size to the crystal lattice.

Many structural electronic and magnetic similarities were found between iridates and cuprates. They simultaneously advance the knowledge of solids with strongly correlated electrons and unconventional superconductors.

This work was carried out at LLB, in collaboration with the Solid-State Physics Laboratory in Orsay.

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