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The authors study epitaxial thin films of the pyrochlore-sublattice compound LiTi2O4 by RIXS and ARPES. They observe cooperation between strong electron correlations and strong electron-phonon coupling, giving rise to a mobile polaronic ground state in which charge motion and lattice distortions are coupled.

Frustrated by reproducibility in electrical measurements on ferroelectric films, Lane Martin, Jon-Paul Maria and Darrell Schlom discuss tactics to reliably synthesize ‘good’ ferroelectric samples, especially in the search for superior materials and device heterostructures.

The intrinsic properties of conventional semiconductors limits the speed and efficiency of field-effect transistors. Here, the authors take advantage of the insulator-to-metal transition in vanadium dioxide to create a transistor with reversible and steep-slope switching at room temperature.

In the absence of matching substrates, the growth of oxide thin films can be challenging. Here, the authors demonstrate the growth of EuO thin films via a topotactic reaction, where a chemical reaction transforms a single crystal of one phase into that of another.

Ferroelectric materials are characterized by a spontaneous polarization, which in practical applications is manipulated by an electric field. This study examines how defects affect the switching with atomic resolution, by usingin situaberration-corrected transmission electron microscopy.

Controlling structures at the atomic level provides an opportunity to design and understand catalysts. Here the authors use thin-film deposition to fabricate perovskite heterostructures in a non-equilibrium manner to assess the effects on electrocatalytic activity for oxygen reduction.

Superconductivity and magnetism have often been regarded as opposites. High magnetic fields usually destroy the superconducting state. But for superconductors constrained to two dimensions, a parallel magnetic field can actually enhance superconductivity.

Here the authors investigate lipid nanodiscs as drug carriers for antitumour immunotherapy. They demonstrate that flexible lipid nanodiscs functionalized with STING-activating cyclic dinucleotides exhibit superior tumour penetration and tumour cell uptake compared with spherical liposomes, resulting in improved antitumour T-cell priming and tumour regression.

The authors report resonant soft x-ray scattering and polarimetry measurements on epitaxial thin films of La3Ni2O7. They find a diagonal bicollinear double spin stripe order, with no evidence of charge modulation.

Negative pressure in ferroelectric nanowires has been achieved by exploiting a phase transformation between crystal structures with differing densities, leading to substantial property enhancement.

The intratumoural injection of recombinantly expressed cytokines bound tightly to the common vaccine adjuvant aluminium hydroxide leads to weeks-long retention of the cytokines in the tumours with minimal side effects, as shown in multiple syngeneic mouse models.

Propelled by the recent renaissance of oxides, a material has emerged with sufficient purity and perfection to join those select materials that show the fractional quantum Hall effect: ZnO.

Electric fields offer an innovative means of controlling condensed-matter systems. The approach has been applied to nanoscale oxide interfaces, for studying the physics of two-dimensional superconductors.

The formation of a two-dimensional electron liquid at the interface between two insulating oxides, now extended to oxides on Si, joins a wealth of observations that reveal how electron transfer between layers is responsible for this unusual effect.

Strain can modify properties, but to prevent cracking is limited to films below a critical thickness. Here, by inserting atomic layers into a ferroelectric superlattice, chemical pressure is generated in thicker films, with enhanced figure of merit for tuneable millimetre-wave dielectrics.

La-substitution in BiFeO₃ enables an electric field-driven conversion of a multi-domain into a single ferroelectric domain accompanied by a single variant spin cycloid. A single domain multiferroic generates 400% larger non-local inverse spin Hall voltage at the output.

The discovery of a highly resistive ferrite magnet where a low magnetic field induces a ferroelectric polarization at room temperature is a key advance towards applications of magnetoelectric coupling.

Oxide superlattices reveal emergent phenomena if the balance between competing degrees of freedom is altered. In this Review, synthetic approaches to tap the properties of competing ground states are described, focusing on two examples — one example yielding a room-temperature multiferroic and a second producing polarization skyrmions.

The striped polarization domains in a BiFeO₃/TbScO₃ heterostructure induce alternating p- and n-type doping at the interface, giving rise to strongly anisotropic in-plane conductance.

The electronic interactions at the interface of oxide materials promise properties that can be very different from those of the parent compounds. The finding that many-body interactions in oxide superlattices can be used to engineer electronic properties offers a new strategy for designing oxide heterostructures.

Cantilevers made of SrTiO₃ grown on silicon use the flexoelectric effect to achieve electromechanical performances similar to piezoelectric bimorph cantilevers.

Understanding the thermal transport properties of superlattice structures is relevant to a number of possible practical applications. Now, the scattering of phonons in oxide superlattices is shown to undergo a crossover from an incoherent to a coherent regime, which in turn strongly alters their thermal behaviour.

During a photoinduced phase transition, electronic rearrangements are usually faster than lattice ones. Time-resolved measurements now show that the insulator-to-metal transition in a thin-film Mott insulator is preceded by lattice reconfiguration.

The authors report a modulation of the magnon spin current by electric polarization reversal.

Authors apply atom probe tomography to image and quantify the 3D distribution of oxygen vacancies in (LuFeO₃)₉/(LuFe₂O₄)₁ superlattices, linking local variations in chemical composition to the emergent multiferroic properties.

The collinear antiferromagnet ruthenium dioxide (RuO₂) can generate an electric-field-induced spin current with a well-defined tilted spin orientation that is approximately parallel to the Néel vector.

Competing phases in layered complex oxides are believed to be relevant for emergent phenomena, which still await to be witnessed. Here, Stone et al. report direct atomic-scale imaging of a multitude of polar phases in Ruddlesden-Popper oxide thin films, exhibiting diverse phenomena in a single structure.

Electric fields typically break symmetry when applied as a stimulus to materials. Here, by forming a superlattice of BiFeO₃ and TbScO₃, it is shown that an electric field can repeatedly stabilize mixed-phase polar and antipolar BiFeO₃.

State-of-the-art electron energy-loss spectroscopy in a transmission electron microscope maps the detailed phonon spectra of single defects in silicon carbide

A universal mechanical exfoliation method of creating freestanding membranes of complex-oxide materials with different crystal structures and orientations and stacking them to produce a range of artificial heterostructures with hybridized physical properties is described.

The control of the magnetic order by optical pulses is of practical relevance for information storage as well as of fundamental interest to understand magnetic processes. Here, the authors demonstrate the control of magnetic order by changing the carrier density in Eu_1−xGd_xO via resonant photoexcitation.

Adding atoms to a semiconductor can improve its electronic properties. In an oxide, taking atoms away can have a similar electronic effect — one that could, it seems, be exploited in device applications.

A real-space imaging technique that combines scanning transmission electron microscopy with an angle-resolved pixellated fast-electron detector is used to image the charge distribution in SrTiO₃, BiFeO₃ and the junction between them.

Understanding the inner workings of complex magnetoelectric multiferroics remains a challenge, as macroscopic techniques characterize average responses rather than the role of individual iron centers. Here, the authors reveal the origin of high-temperature magnetism in multiferroic superlattices.

Ruthenium oxide has attracted recent interest as a non-superconducting material where superconductivity can be induced by epitaxial strain. Here, the authors explore strained (100)-oriented RuO₂ films on TiO₂(100) substrate and reveal strain-induced superconductivity similarly to strained RuO₂(110) films, providing insights into the thickness-dependence and electronic structure mechanisms of superconductivity.

How the electronic structure of a mixed-valence system changes with respect to local chemical environment remains elusive. Here, Chatterjee et al. show that valence fluctuations of YbAl₃ can lead to dramatic changes in the Fermi surface topology in reciprocal space.

In complex oxides, oxygen octahedra are major structural motifs and their tilts sensitively determine the material’s physical properties. Exploiting Coherent Bragg Rod Analysis enables 3D mapping of complex tilt patterns and reveals the means to control polarization through them in CaTiO₃ thin films.

A new family of tunable microwave dielectrics with unparalleled performance at frequencies up to 125 GHz at room temperature has been created, using dimensionality to add and control a local ferroelectric instability in a system with exceptionally low dielectric loss.

A single-phase multiferroic material is constructed, in which ferroelectricity and strong magnetic ordering are coupled near room temperature, enabling direct electric-field control of magnetism.

Ferroelectric ferromagnets — materials that are both ferroelectric and ferromagnetic — are of significant technological interest. But they are rare, and those that do exist have weak ferroelectric and ferromagnetic properties. Recently a new way of fabricating such materials was proposed, involving strain from the underlying substrate. This route has now been realized experimentally for EuTiO₃. The work shows that a single experimental parameter, strain, can simultaneously control multiple order parameters.