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Title: Electronic confinement and instabilities in layered perovskites
Abstract:
The family of ABO3 perovskites have long been a central pillar of functional oxide materials research, because of their structural flexibility (where the A and B sites can be occupied almost any transition metal ion), enabling it to host many different electronic and magnetic phases, including ferroelectricity, (anti-) ferromagnetism and metal-insulator transitions. Beyond the cubic perovskite structure, ABO₃ serves as the parent structure for a range of layered perovskite phases, where perovskite layers are separated by spacers, resulting a confinement of electronic degrees and structural degrees of freedom. In this talk, I will discuss different types of layered perovskite structures, showing how the confinement of the perovskite blocks within layered structure enables novel electronic and magnetic properties.
In particular, I will discuss two novel series of layered materials. First, the layered tungsten phosphates, where the layered structure stabilizes a 2D electron gas through electronic confinement and polar distortions within the otherwise insulating tungsten layers—a phenomenon
we term “anti-polar 2D metallicity” [1].
Then I will present our research on the layered Ruddlesden-Popper chromates (Srn+1CrnO3n+1) where I show how the dimensional confinement enables an orbital ordering within the Cr d-orbitals
that triggers a metal-insulator transitions in the n = 1 and n = 2 compounds [2]. This has a particular impact on the magnetic properties of the system, as this distortion breaks the lattice’s translational symmetry, lifting the degeneracy of spin-up and spin-down bands — a phenomenon known as altermagnetism[3]. We explore the manifestation of altermagnetism within the chromate series and its dependence on the number of layers. Through these two examples, I aim to offer a glimpse into novel functionalities that can be achieved in layered perovskite materials.
[1] H Nimoh, Q.N. Meier, et al, JACS 146 (34), 23955-23962 (2024)
[2] S. Doyle, Q.N. Meier et al, Phys. Rev. Mater 8, L071602 (2024)
[3] L. Šmejkal, J. Sinova, and T. Jungwirth, Phys. Rev. X 12, 040501 (2022)
