C08

Spin-orbit coupling and electron correlations in complex oxides

Summary

While the overarching theme continues to be the study of the generic phase diagram spanned by correlation strength and spin-orbit coupling, in the next funding period we will investigate 4d transition metal compounds in addition to the 5d iridates already in focus, and abandon the study of corre- lated 3d oxides. The goal is to exploit the capabilities of thin film growth — mainly accomplished by pulsed laser deposition — to create and tune emergent, spin-orbit entangled electronic phases such as spin-orbit Mott insulators, quantum spin liquids, and correlated topological semimetals, and to ultimately implement the associated functionalities in devices. To identify and characterize such phases we will employ high-energy spectroscopies, in particular photoelectron spectroscopy using soft and hard x-rays, and (magneto)transport measurements augmented by advanced transmission electron microscopy as well as theoretical input in terms of materials specific calculations. As for the iridates, we will continue our work on the growth of SrIrO3 thin films with (111) orientation which due to their buckled honeycomb type of lattice can be viewed as graphene-like but with correlated d-electrons. In addition, we plan to investigate the compound CaIrO3 which has been reported to be a Dirac line-node semimetal with correlation-tunable — in our approach to be realized via the layer thickness — high-mobility electrons exhibiting an unusually high magnetoresistance. Regarding 4d compounds, we will continue our ongoing studies of polar/non-polar LaAlO3 /SrRuO3 , in particular the observation of signatures of the anomalous Hall effect, to verify the claim of a topological phase transition of the band structure induced by charge pinning at the interface upon electronic reconstruc- tion and accompanied by a sign change in the anomalous Hall conductivity. Furthermore, we plan to explore d1 SrNbO3 thin films that will be strain- and thickness-tuned to become a Dirac semimetal with large spin-orbit coupling. Unusual transport properties with a magnetoresistance of 150,000% have been reported when the film thickness is optimally adjusted. The outlined research program will strongly benefit from collaborations that have been established within the SFB, in particular with C05, C10, and Z02 (to be continued outside the SFB 1170, viz. with the RCCM), as well as with external partners focusing on transport and advanced transmission electron microscopy.