The recent discovery of superconductivity at the interfaces between KTaO 3 and EuO (or LaAlO 3 ) gives birth to the second generation of oxide interface superconductors. This superconductivity exhibits a strong dependence on the surface plane of KTaO 3 , in contrast to the seminal LaAlO 3 /SrTiO 3 interface, and the superconducting transition temperature T c is enhanced by one order of magnitude. For understanding its nature, a crucial issue arises: Is the formation of oxide interfaces indispensable for the occurrence of superconductivity? Exploiting ionic liquid (IL) gating, we are successful in achieving superconductivity at KTaO 3 (111) and KTaO 3 (110) surfaces with T c up to 2.0 and 1.0 K, respectively. This oxide-IL interface superconductivity provides a clear evidence that the essential physics of KTaO 3 interface superconductivity lies in the KTaO 3 surfaces doped with electrons. Moreover, the controllability with IL technique paves the way for studying the intrinsic superconductivity in KTaO 3 .

A nanocomposite consisting of one‐dimensional copper nanowires and two‐dimensional reduced graphene oxide nanosheets (CuNWs/rGO) was synthesized by a simple one‐step wet‐chemical synthetic process. The Cu NWs anchored onto the rGO nanosheets with wrinkles and folds had a smooth surface. The CuNWs/rGO hybrids exhibited excellent electrocatalytic activity toward glucose oxidation due to the superior conductivity along one‐dimensional direction and excellent catalytic activity of Cu NWs and rapid electron transfer in the two‐dimensional rGO sheets. A wide linear range up to 11 mM, high sensitivity (1625 µA/(mM ⋅ cm2)), low detection limit (0.2 µM) and fast response (<2 s) to glucose oxidation were obtained under a working potential of 0.58 V for the hybrid with optimized Cu/rGO mass ratio in the alkaline solution. Furthermore, the CuNWs/rGO composites displayed high selectivity to glucose and resistance against poisoning by commonly interfering species such as ascorbic acid, dopamine, uric acid, acetamidophenol and some carbohydrates. The CuNWs/rGO hybrids with good reproducibility, stability and poisoning resistance to chloride ions were therefore promising for the potential application as non‐enzymatic amperometric glucose sensors with improved electrochemical performances.

In a seminal work, Gozar et al. reported on the high-temperature interface superconductivity in bilayers of insulating La 2 CuO 4 and metallic La 2−x Sr x CuO 4 (x=0.45). An interesting question to address is how general and robust this interface superconductivity is. In the past, the cuprate bilayers were grown in a unique atomic-layer molecular beam epitaxy system, with a Sr doping range of x≤0.47, and the atomically flat interface was thought to be indispensable. Here, we have fabricated bilayers of La 2 CuO 4 and La 2−x Sr x CuO 4 by pulsed laser deposition. We have tried to extend the nominal doping range of Sr from the previous maximum of 0.47 to the present 1.70 (the nominal Sr content in the targets). X-ray diffraction result indicates that our La 2−x Sr x CuO 4 films with x≤0.60 have very high crystalline quality; but the film crystalline structure degrades gradually with further increasing x, and finally the structure is fully lost when x reaches 1.40 and higher. Although the film quality scatters dramatically, our experiments show that there exists superconductivity for bilayers in nearly the entire over-doped Sr range, except for a non-superconducting region at x~0.80. These observations demonstrate that the interface superconductivity in copper oxides is very general and robust.

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High-temperature superconductivity in cuprates is a great surprise in quantum materials and its mechanism remains a puzzle. It has been a longstanding challenge to understand how the versatile phenomena exhibited in these materials, such as the pseudogap (PG) and strange metal states, together with a plethora of exotic electronic orders, coexist and compete with superconductivity. Among them, charge order (CO) is found to be ubiquitous in underdoped cuprates, which competes with superconductivity and is suggested for connecting to the pseudogap phase. On the other hand, the extremely overdoped cuprates are generally considered as Fermi liquid metals without exotic orders. Contrary to the conventional wisdom, here we reveal charge order in extremely overdoped La2−xSrxCuO4 (0.35 ≤ x ≤ 0.6), beyond the superconducting dome using resonant soft x-ray scattering spectroscopy. This CO has a periodicity of ∼ 6 lattice units with correlation lengths of ∼ 3 -20 lattice units and persists up to 300 K. This CO cannot be explained by either the Fermi surface instability or the doped Hubbard model, suggesting correlation effects originating from other interactions in the highly overdoped regimes. Our findings reveal that CO is prevailing in the overdoped metallic regime and distinct from the pseudogap phase ending at x = 0.19. Our results suggest that high-temperature superconductors can be obtained by doping charge-ordered metals in addition to doped Mott insulators, providing a new perspective for understanding the dome-shaped superconducting phases.