Special Solid State & Optics Seminar
sponsored by “The Flint Fund Series on Quantum Devices and Nanostructures”
Tuesday, February 28th at 10:30 AM
Dr. Harold Hwang, Stanford University
Mason 107 or via Zoom
Meeting ID: 999 6490 1791
Password: 327241
Zoom Link: https://yale.zoom.us/j/99964901791?pwd=eXdYbVYwRTRVOFBaSGFHMStkdFJkdz09
Correlated States in Infinite Layer Oxides
We present two recent developments of quantum materials in the infinite layer structure, which are synthesized using topochemical reduction reactions in thin film heterostructures. The first example is doped layered nickelates, which exhibits superconductivity [1], strong magnetic fluctuations [2], instabilities towards charge stripes [3], and a landscape of unusual normal state properties from which superconductivity emerges [4]. These features are strongly reminiscent of the cuprates, despite key differences in the electronic structure and the absence of a proximate correlated insulator. The second example is recent progress on CaCoO2, the first case of a cobalt oxide stabilized in the infinite layer structure [5]. We observe a dramatically distorted structure, with Angstrom-scale displacements of the cations from their high-symmetry positions.
This can be understood to originate from the Jahn-Teller degeneracy of the dxz and dyz-orbitals in the d7 electronic configuration, along with substantial ligand-transition metal mixing. A complex pattern of distortions arises in a 2√2× 2√2×1 tetragonal supercell, reflecting the competition between an ordered Jahn-Teller effect of the CoO2 sublattice, and geometric frustration of the associated displacements of the Ca sublattice. As a result of this competition, the CaCoO2 structure forms an extended two-in/two-out type of Co distortion following “ice rules”.
[1]Danfeng Li et al., Nature 572, 624 (2019).
[2]Haiyu Lu et al., Science 373, 213 (2021).
[3]Matteo Rossi et al., Nat. Phys. 18, 869 (2022).
[4]Kyuho Lee et al., arXiv: 2203.02580.
[5]Woojin Kim et al., in press.
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Event time:
Tuesday, February 28, 2023 - 10:30am
Hosted By:
Yu He