Giant Jahn-Teller distortion in geometrically frustrated infinite layer lattice
일 시 : 2022년 01월 03일 목요일 16:00
연 사 : 김 우 진 박사 (Stanford University)
장 소 : 자연과학관 747호 & 온라인 (줌 회의ID: 811 0183 4598 , 암호: 783734)
HOST : 문 순 재 교수님
초 록
The Jahn-Teller effect, in which electronic configurations with energetically degenerate orbitals induce lattice distortions to lift this degeneracy, plays a key role in many symmetry-lowering crystal deformations. While many examples occur in octahedrally or tetrahedrally coordinated transition metal oxides, due to their high orbital degeneracy, this effect has yet to be manifested for square-planar coordination, as found in infinite layer Cu, Ni, and Fe oxides.1-3 Within this quasi-2D structure, how orbital degeneracy would affect the crystal and electronic structure is an open experimental question. To answer this, we stabilized a new type of infinite-layer cobaltate which has orbital degeneracy within square-planar coordination. We observe a dramatically distorted infinite layer structure, with Angstrom-scale displacements of the cations from their high-symmetry positions. The details of crystalline structure of infinite-layer cobaltate and its possible electronic ground state will be discussed.
[1] T. Siegrist et al., Nature 334, 231–232 (1988).
[2] M. A. Hayward, et al., J. Am. Chem. Soc. 121, 8843–8854 (1999).
[3] Y. Tsujimoto et al., Nature 450, 1062–1065 (2007).