New physics in iridium compounds

New physics in iridium compounds: The researchers looked at the electronic structure of Sr3CuIrO6, a compound in which the iridium atoms are surrounded by oxygen atoms in a slightly distorted octahedron.

Such a system is typically modeled by assuming that the octahedron is perfectly regular and thus the orbital degree of freedom is being quenched in certain ways. If the shape is not perfect, then the layout of the electron cloud is deformed, but previous research groups have assumed that minor irregularities made little difference and could be ignored. In this case, the structure of Sr3CuIrO6 is close to the ideal.

When the Brookhaven-led group gathered data on the actual structure, however, they found that the irregularity makes a noticeable and important change to the wave function, which thus deforms the orbitals of the active electrons, as shown in the graphic. When the spin couples to the orbitals, the effect cannot be ignored.