Speaker
Description
There are two known superconducting nickelate families, i.e. low-
valence Ni($3𝑑^{9−\delta}$) compounds and Ruddelsden-Popper (RP) materials with Ni($3𝑑^{8-\delta}$) valence. While both families host NiO$_2$ square
planes, key difference is given by the missing apical oxygen atoms in
the low-valence nickelates. A possible route to connect both nickelate
families might be given by the reduction of the La$_3$Ni$_2$O$_7$ RP bilayer compound, i.e. by removing it’s apical oxygens. Complete removal
results in the La$_3$Ni$_2$O$_6$ compound, while taking out only half of the apical oxygens results in the La$_3$Ni$_2$O$_{6.5}$ system. Those reduced materials are so far only scarcely characterized experimentally, but display quite intriguing correlation physics from theory. We will discuss the results of advanced first-principles many body calculations for correlated electrons in the different bilayer nickelates, highlighting variations in the mechanisms at strong coupling as well as the challenging low-temperature physics.