Symmetry Breaking, Orbitals and Macroscopic Properties of Correlated Oxides

by Prof. Lior Kornblum

Technion - Israel Institute of Technology

at Condensed Matter Seminar

Mon, 26 Feb 2024, 11:10
Sacta-Rashi Building for Physics (54), room 207

Abstract

Electron correlation is responsible for countless interesting condensed matter phenomena. Oxides with electron correlation provide an attractive testbed for many of those, where coupling between the spin, charge and lattice degrees of freedom can be played with. We consider strontium vanadate (SrVO3) as a simple test case of the Mott-Hubbard type of correlated electronic structure. The relative simplicity stems from its d1 electronic configuration and high-symmetry cubic perovskite structure. We harness advanced thin film synthesis techniques to control of the correlation strength by tuning the degree of orbital overlap using picometer-scale lattice engineering. We illustrate how bandwidth control and concurrent symmetry breaking can govern the electronic structure of this SrVO3 model system. This study shows how tensile and compressive biaxial strain oppositely affect the SrVO3 in-plane and out-of-plane orbital occupancy, resulting in the partial alleviation of the orbital degeneracy. The spectral weight redistribution under strain is derived and explained, illustrating how tensile strain drives the system toward a Mott insulating state. This picture, derived from a simple and clean system, can shed light on other more complex examples.
Should time permit, I will present recent results on the role and mechanism of symmetry breaking in the magnetic anisotropy of Ru-substituted manganite films. We uncovered tilted magnetic anisotropy in slightly compressively-strained films, which includes strong perpendicular magnetization in addition to surprising in-plane anisotropy. With detailed microstructural characterization we are able to pinpoint the microstructural origins of both axes of anisotropy, and speculate on possible Mn-Ru exchange mechanisms. We then employed x-ray magnetic circular dichroism to pinpoint the exchange mechanism and shed light on the atomic origins of the anisotropy. These results pave to way to designing materials with technologically-attractive types of magnetic anisotropy having a near-room-temperature Curie temperatures.

Created on 20-02-2024 by Naamneh, Muntaser (mnaamneh)
Updaded on 20-02-2024 by Naamneh, Muntaser (mnaamneh)