More than 30 years after the discovery of cuprates, no consensus has been achieved about the origin of HTS. Layered nickelates can help shed light on this problem. The left panel shows the structure of the infinite-layer nickelate RNiO2 (R=rare-earth) with NiO2 planes that has recently been found to be superconducting. The right panel shows the layered nickelate phase diagram with respect to 3d electron count. The vertical lines show layered nickelates with different n (n being the number of NiO2 planes along the c-axis).
2D magnets
Until recently, 2D magnetism remained elusive since the existence of magnetic order in 2D is a priori not guaranteed. The story changed in 2016 when two groups provided evidence of antiferromagnetism in monolayers of FePS3. In 2017, the presence of ferromagnetic order was proven in monolayers of CrI3 and on a bilayer of Cr2Ge2Te6. The list of candidates has been growing ever since.
