UPt3, heavy fermions and superconductivity

Pb10-xCux(PO4)6O: a Mott or charge transfer insulator in need of further doping for (super)conductivity

We briefly review the status quo of research on the putative superconductor Pb9Cu(PO4)6O also known as LK-99. Further, we provideab initioderived tight-binding parameters for a two- and five-band model, and solve these in dynamical-mean-field theory. The interaction-to-bandwidth ratio makes LK-99 a Mott or charge transfer insulator. Electron or hole doping (which is different from substituting Pb by Cu and thus differs from LK-99) is required to make it metallic and potentially superconducting.

Half-metallicity in uranium intermetallics: crystal structure prediction of a high-pressure phase of UCo

Evolutionary crystal structure prediction methods combined with density functional theory (DFT) calculations reveal a high-pressure (hp) phase of the intermetallic compound UCo crystalizing in the NaTl structure type ([Formula: see text]). We predict this compound to be formed at pressures below 9 GPa. Hp-UCo shows the same structural trends as the two experimentally known pseudo-binary compounds UCo_0.2Rh_0.8 and UNi_0.8Pt_0.2. We classify them as ordered solid solutions of a bcc lattice following Vegard's law. We predict hp-UCo and its adjacent phases UFe and UNi to be itinerant magnets. In the limit of vanishing spin-orbit interactions UFe and hp-UCo are half-metallic ferrimagnets. Spin-orbit coupling generally reduces the spin-polarization at the Fermi level. In case of hp-UCo the decrease depends on the applied DFT functional making the prediction of actual occurrence of half-metallicity problematic. In case of UFe the results are less dependent on the DFT functional. We demonstrate with these calulations that against 'common sense' also materials with heavy elements can be interesting candidates for half-metallicity. We highlight that the NaTl structure type should be an interesting candidate for further investigations of half-metallicity.