A superconducting interface: Interfaces between materials can harbor quantum states that belong to neither of the materials. A classic example is the superconducting interface between two insulating oxides, LaAlO ₃ and SrTiO ₃ , with a critical temperature of around 200 millikelvin. Liu et al. observed superconductivity at a different interface—formed between KTaO ₃ as a substrate and an overlayer of either EuO or LaAlO ₃ —at a considerably higher temperature of about 2 kelvin. Transport measurements displayed anisotropy, which may indicate an unusual superconducting state. Science , this issue p. 716

Controlling interfacial superconductivity: The interface between the oxides LaAlO ₃ and KTaO ₃ (111) has been shown to superconduct at temperatures up to 2 Kelvin. Chen et al. show that this superconductivity can be controlled with electric fields. As they tuned the gating voltage, the researchers observed a dome-shaped variation of the superconducting critical temperature. This variation could not be ascribed to the change in carrier density, but rather seemed to reflect the change in the mobility of the carriers. Science , this issue p. 721

The Rashba physics has been intensively studied in the field of spin orbitronics for the purpose of searching novel physical properties and the ferromagnetic (FM) magnetization switching for technological applications. We report our observation of the inverse Edelstein effect up to room temperature in the Rashba-split two-dimensional electron gas (2DEG) between two insulating oxides, SrTiO₃ and LaAlO₃, with the LaAlO₃ layer thickness from 3 to 40 unit cells (UC). We further demonstrate that the spin voltage could be markedly manipulated by electric field effect for the 2DEG between SrTiO₃ and 3-UC LaAlO₃. These results demonstrate that the Rashba-split 2DEG at the complex oxide interface can be used for efficient charge-and-spin conversion at room temperature for the generation and detection of spin current.

Two-dimensional (2D) van der Waals (vdW) magnets have recently attracted increasing attention, as they provide a novel system for exploring 2D magnetism. However, intrinsic ferromagnetism in 2D systems has almost exclusively been observed at low temperatures, limiting their technological relevance. ${\mathrm{Fe}}_{\mathrm{N}}{\mathrm{Ge}\mathrm{Te}}_2$ ($N=3$, 4, and 5) systems are currently becoming the most attractive 2D vdW materials due to their relatively high Curie temperatures and large saturation magnetization. However, the nature of their complex yet intriguing magnetic behaviors is still unclear, in part due to the multiple inequivalent iron sites and iron vacancies. Here, we show evolution of magnetic ordering transitions in ${\mathrm{Fe}}_{5-x}{\mathrm{Ge}\mathrm{Te}}_2$ with high Curie temperature and a strong saturation magnetization using photoemission electron microscopy and transport measurements. At 275 K, the ferromagnet transitions to a ferrimagnet, and below 110 K transitions to a state with glassy clusters. These are evidenced from temperature-dependent magnetic stripe domain evolution and anisotropic magnetoresistance measurements. Our findings show a clear magnetic ground state of ${\mathrm{Fe}}_{5-x}{\mathrm{Ge}\mathrm{Te}}_2$ at room temperature which signals that ${\mathrm{Fe}}_{5-x}{\mathrm{Ge}\mathrm{Te}}_2$ system is a very promising candidate for spintronic devices and provides a material design pathway to further increase the Curie temperature and saturation moments in vdW ferromagnets.

We report on the observation of a $T_c\sim 0.9\mathrm{K}$ superconductivity at the interface between ${\mathrm{LaAlO}}_3$ film and the $5d$ transition metal oxide ${\mathrm{KTaO}}_3(110)$ single crystal. The interface shows a large anisotropy of the upper critical field, and its superconducting transition is consistent with a Berezinskii-Kosterlitz-Thouless transition. Both facts suggest that the superconductivity is two-dimensional (2D) in nature. The carrier density measured at 5 K is $\sim 7\times {10}^{13}{\mathrm{cm}}^{-2}$. The superconducting layer thickness and coherence length are estimated to be $\sim 8$ and $\sim 30\mathrm{nm}$, respectively. Our result provides a new platform for the study of 2D superconductivity at oxide interfaces.

Two-dimensional electron gases (2DEGs) at oxide interfaces, which provide unique playgrounds for emergent phenomena, have attracted increasing attention in recent years. While most of the previous works focused on the 2DEGs at ${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$ interfaces, here we report on a new kind of 2DEGs formed between a magnetic insulator EuO and a high-$k$ perovskite ${\mathrm{KTaO}}_3$. The 2DEGs are not only highly conducting, with a maximal Hall mobility of $111.6{\mathrm{cm}}^2/\mathrm{V}\mathrm{s}$ at 2 K, but also well spin polarized, showing strongly hysteretic magnetoresistance up to 25 K and well-defined anomalous Hall effect up to 70 K. Moreover, unambiguous correspondences between the hysteretic behaviors of 2DEGs and the EuO layer are captured, suggesting the proximity effect of the latter on the former. This is confirmed by the results of density-functional theory calculations: Through interlayer exchange, EuO drives the neighboring ${\mathrm{TaO}}_2$ layer into a ferromagnetic state. The present work opens new avenues for the exploration for high performance spin-polarized 2DEGs at oxide interfaces.