Karsten Held, TU Wien
Nickelate superconductors calculated by dynamical vertex approximation
New hope for a better understanding of high-temperature superconductivity arose with the discovery of superconductivity in nickelates. These new superconductors are at the same time strikingly similar to cuprates but also decisively different,
an ideal combination to discriminate the essentials from the incidentals for superconductivity in both systems.
Using the dynamical vertex approximation and a minimal single-band Hubbard model plus electron pockets that merely act as charge reservoirs, we have predicted the phase diagram of nickelate superconductors in excellent agreement with
experiment after defect-free films could be synthesized. This includes the quantitative value of Tc, the doping region of the dome and its skewness. Also pentalayer nickelates seamlessly fit.
Our calculations also provides new insight into how to increase Tc. We find the sweet spot for a high Tc to lie actually at a smaller interaction-to-hopping ratio U/t. One way to achieve this is replacing 3d nickelates by 4d palladates. Another route is applying pressure. Here, we reproduce the experimentally observed increase of Tc with pressure, measured so-far up to 12 GPa in Sr0.18Pr0.82NiO2. We predict, Tc will further increase with a maximum around 50 GPa. Even more remarkably, the parent compound PrNiO2 itself will become superconducting under pressure thanks to the self-doping of the Ni dx2−y2 orbital, with a calculated maximal Tc close to 100K.
Giorgio Sangiovanni, University of Würzburg
In the recent literature, the concept of topological Mott insulator has been spelled out in rather different ways. Due to the intrinsic many-body nature, a comprehensive classification is challenging to formulate. In this talk I will discuss a novel, remarkably simple way of describing topological Mott insulators based on the momentum dispersion of single-particle Green’s function zeros. After focusing on the fate of the bulk-boundary correspondence, I will propose a way of revealing the physical consequences of the boundary zeros based on the hybridization with conventional topologically protected edge modes.