The nature of electron-electron and electron-lattice interactions in metallic oxides is revised. The common wisdom is that the strong correlations among electrons determine their properties. Here we argue that the unavoidable coupling between free electrons and the lattice in ionic materials leads to the formation of polarons. These are carriers dressed by a lattice distortion that travel with them and largely determine the transport and some optical properties.
Moreover, we argue that in early transition metal oxides, the Fermi surface has a cylindrical shape that limits the phonons available for scattering. Taking SrVO3 as illustrative example of a Fermi liquids, we demonstrate that both mechanisms can contribute to the ubiquitously observed quasi-T2 temperature dependence of the electrical resistivity in many metallic oxides. A new twist on the physics of Fermi liquids in ionic lattices.
Oxides for new-generation electronics
Electron–Phonon Coupling and Electron–Phonon Scattering in SrVO3
From catalysis and flat panel displays to photovoltaics, transparent and conducting transition metal oxides are gaining momentum toward more sustainable and cost-efficient applications. Here it is shown that, without using phase-matching arrangements, bulk plasmons can be excited in continuous epitaxial films of metallic SrVO3 and SrNbO3, with plasma absorption edges at visible range, and tuned mainly by electron correlations and phonon dressing. Films can be made reflective or transparent at whish.
The incorporation of the new peakness-enhancing fast Fourier transform compatible ipp procedure (ipp = inner-pixel preservation) into the recently published SM algorithm based on |ρ| [Rius (2020). Acta Cryst A76, 489–493] improves its phasing efficiency for larger crystal structures with atomic resolution data. Its effectiveness is clearly demonstrated via a collection of test crystal structures (taken from the Protein Data Bank) either starting from random phase values or by using the randomly shifted modulus function (a Patterson-type synthesis) as initial ρ estimate.
The research into insulating ferrimagnetic garnets has gained enormous momentum in the past decade. This is partly due to the improvement in the techniques to grow high-quality ultrathin films with desirable properties and the advances in understanding the spin transport within the ferrimagnetic garnets and through their interfaces with conducting materials. In recent years, we have seen remarkable progress in controlling the magnetization state of ferrimagnetic garnets by electrical means in suitable heterostructures and device architectures.
Systematic studies on polycrystalline Hf1–xZrxO2 films with varying Zr contents show that HfO2 films are paraelectric (monoclinic). If the Zr content is increased, films become ferroelectric (orthorhombic) and then antiferroelectric (tetragonal). HfO2 shows very good insulating properties and it is used in metal-oxide-semiconductor field-effect devices, while ZrO2 shows good piezoelectric properties, but it is antiferroelectric. In between, Hf0.5Zr0.5O2 shows good ferroelectric properties at the expense of poorer insulating and piezoelectric properties than HfO2 and ZrO2, respectively.
About ten years after ferroelectricity was first reported in doped HfO2 polycrystalline films, there is tremendous interest in this material and ferroelectric oxides are once again in the spotlight of the memories industry. Great efforts are being made to understand and control ferroelectric properties. Epitaxial films, which have fewer defects and a more controlled microstructure than polycrystalline films, can be very useful for this purpose. Epitaxial films of ferroelectric HfO2 have been much less investigated, but after the first report in 2015 significant progress has been achieved.