Superlattice approach to doping infinite-layer nickelates

The recent observation of superconductivity in infinite-layer Nd$_{1-x}$Sr$_x$NiO$_2$ thin films has attracted a lot attention, since this compound is electronically and structurally analogous to the superconducting cuprates. Due challenges phase stabilization upon chemical doping with Sr, we synthesized artificial superlattices LaNiO$_3$ embedded insulating LaGaO$_3$, used layer-selective topotactic reactions reduce nickelate layers LaNiO$_{2}$. Hole achieved via interfacial oxygen atoms tuned layer thickness. We electrical transport measurements, transmission electron microscopy, x-ray spectroscopy together ab initio calculations track changes local nickel electronic configuration reduction found that these are reversible. Our experimental theoretical data indicate doped holes trapped at quadratic pyramidal Ni sites. Calculations for electron-doped cases predict different behavior, evenly distributed electrons among layers, thus opening up interesting perspectives transition metal oxides.