Modulation of Manganite Nanofilm Properties Mediated by Strong Influence of Strontium Titanate Excitons

Abstract

Hole-doped perovskite manganites have attracted much attention because of their unique optical, electronic, and magnetic properties induced by the interplay between spin, charge, orbital, and lattice degrees of freedom. Here, a comprehensive investigation of the optical, electronic, and magnetic properties of LaSrMnO thin films on SrTiO (LSMO/STO) and other substrates is conducted using a combination of temperature-dependent transport, spectroscopic ellipsometry, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism. A significant difference in the optical property of LSMO/STO that occurs even in thick (87.2 nm) LSMO/STO from that of LSMO on other substrates is discovered. Several excitonic features are observed in thin film nanostructure LSMO/STO at ∼4 eV, which could be attributed to the formation of anomalous charged excitonic complexes. On the basis of the spectral weight transfer analysis, anomalous excitonic effects from STO strengthen the electronic correlation in LSMO films. This results in the occurrence of optical spectral changes related to the intrinsic Mott-Hubbard properties in manganites. We find that while lattice strain from the substrate influences the optical properties of the LSMO thin films, the coexistence of strong electron-electron (e-e) and electron-hole (e-h) interactions which leads to the resonant excitonic effects from the substrate plays a much more significant role. Our result shows that the onset of anomalous excitonic dynamics in manganite oxides may potentially generate new approaches in manipulating exciton-based optoelectronic applications.

Modulation of New Excitons in Transition Metal Dichalcogenide‐Perovskite Oxide System

“…The absorption coefficient, α, of MoS 2 monolayer was extracted from parameters Ψ and Δ utilizing an air/MoS 2 /STO (or Al 2 O 3 ) multilayer model, where monolayer-MoS 2 consisted of a homogeneously uniform medium [14,23] and a composite heterointerface component. A. Woollam Co., Inc spectroscopic ellipsometer with photon energy of 0.6-4.5 eV was used to measure the ellipsometry parameters Ψ (the ratio between the amplitude of p and s-polarized reflected light) and Δ (the phase difference between p and s-polarized reflected light) in a high vacuum chamber with a base pressure of 1 × 10 −9 mbar.…”

“…The substrate layers (bulk SrTiO 3 or Al 2 O 3 ) were also measured under the same conditions. The absorption coefficient, α, of MoS 2 monolayer was extracted from parameters Ψ and Δ utilizing an air/MoS 2 /STO (or Al 2 O 3 ) multilayer model, where monolayer‐MoS 2 consisted of a homogeneously uniform medium and a composite heterointerface component.…”

“…Previous study has shown that high‐energy resonant excitons are present in the SrTi 1‐ x Nb x O 3 family . Intriguingly, the resonant excitons interact strongly with a graphene layer or manganite film via their interfacial interactions and thereby affect the electronic and optical properties of these materials . It shows that the excitons from SrTiO 3 (STO) substrate can even propagate ≈87 nm into the top manganite thin‐film systems .…”

“…[14] This provides an exciting opportunity to introduce and manipulate the propagation of excitons from 3D substrate materials to 2D-TMDs. [14] This provides an exciting opportunity to introduce and manipulate the propagation of excitons from 3D substrate materials to 2D-TMDs.…”

“…Intriguingly, the resonant excitons interact strongly with a graphene layer or manganite film via their interfacial interactions and thereby affect the electronic and optical properties of these materials . It shows that the excitons from SrTiO 3 (STO) substrate can even propagate ≈87 nm into the top manganite thin‐film systems . This provides an exciting opportunity to introduce and manipulate the propagation of excitons from 3D substrate materials to 2D‐TMDs.…”