Resonant tunneling driven metal-insulator transition in double quantum-well structures of strongly correlated oxide

Analysis of heavy metal pollution sources caused by sulfide minerals in tunnel waste under photocatalytic oxidation conditions

The rapid expansion of global transportation infrastructure has significantly increased tunnel construction in mountainous regions, generating substantial amounts of sulfide-rich excavation waste. Current disposal practices relying on open-air storage pose critical environmental risks through land occupation and potential heavy metal pollution, while the intrinsic pollutant release mechanisms from sulfide mineral weathering remain insufficiently investigated. This study elucidates a novel pollution pathway through photocatalytic oxidation-triggered heavy metal liberation in tunnel waste. Conducted comprehensive mineralogical characterization of sulfide-bearing tunnel residues and systematically examined heavy metal migration patterns under controlled photooxidative conditions (variable illumination duration, temperature (25-45 °C), moisture content (20-60%), and aeration status). Parallel experiments monitored pH evolution and heavy metal release kinetics, particularly focusing on Cd, As, Cr, Pb, and Mn. Results revealed the presence of photochemically active Fe- and Ti-bearing phases in sulfide matrices that drive acid generation through solar-induced sulfite oxidation. This catalytic process established strongly acidic conditions (pH 2.0 ± 0.3) under optimal parameters: 35 °C, 40% moisture content, and 48-h photoexposure with aeration. The resultant acidification promoted mineral dissolution, yielding maximum leachate concentrations of 0.09 mg/L Cd, 1.8 μg/L As, 0.05 mg/L Cr, 0.36 mg/L Pb, and 8.54 mg/L Mn, representing 3-eightfold increases compared to dark controls. This work provides the first mechanistic evidence of photocatalysis-mediated acid mine drainage formation in tunnel waste systems, challenging conventional geochemical weathering paradigms. The findings establish a theoretical framework for predicting heavy metal pollution risks and inform remediation strategies through photochemical parameter control, ultimately supporting sustainable management of tunnel excavation byproducts.

Hybrid Ferroelectric Tunnel Junctions: State of the Art, Challenges, and Opportunities

Ferroelectric tunnel junctions (FTJs) harness the combination of ferroelectricity and quantum tunneling and thus herald opportunities in next-generation nonvolatile memory technologies. Recent advancements in the fabrication of ultrathin heterostructures have enabled the integration of ferroelectrics with various functional materials, forming hybrid tunneling-diode junctions. These junctions benefit from the modulation of the functional layer/ferroelectric interface through ferroelectric polarization, thus enabling further modalities and functional capabilities in addition to tunneling electroresistance. This Perspective aims to provide in-depth insight into the physical phenomena of several typical ferroelectric hybrid junctions, ranging from ferroelectric/dielectric, ferroelectric/multiferroic, and ferroelectric/superconducting to ferroelectric/2D materials, and finally their expansion into the realm of ferroelectric resonant tunneling diodes (FeRTDs). This latter aspect, i.e., resonant tunneling, offers an approach to exploiting tunneling behavior in ferroelectric heterostructures. We discuss examples that have successfully shown room-temperature ferroelectric control of parameters such as the resonant peak, tunnel current ratio at peak, and negative differential resistance. We conclude the Perspective by summarizing the challenges and highlighting the opportunities for the future development of hybrid FTJs, with a special emphasis on a possible type of FeRTD device. The prospects for enhanced performance and expanded functionality ignite tremendous excitement in hybrid FTJs and FeRTDs for future nanoelectronics.

0.68% of solar-to-hydrogen efficiency and high photostability of organic-inorganic membrane catalyst

Solar-driven flat-panel H2O-to-H2 conversion is an important technology for value-added solar fuel production. However, most frequently used particulate photocatalysts are hard to achieve stable photocatalysis in flat-panel reaction module due to the influence of mechanical shear force. Herein, a highly active CdS@SiO2-Pt composite with rapid CdS-to-Pt electron transfer and restrained photoexciton recombination was prepared to process into an organic-inorganic membrane by compounding with polyvinylidene fluoride (PVDF). This PVDF networked organic-inorganic membrane displays high photostability and excellent operability, achieving improved simulated sunlight-driven alkaline H2O-to-H2 conversion activity (213.48 mmol m-2 h-1) following a 0.68% of solar-to-hydrogen efficiency. No obvious variation in its appearance and micromorphology was observed even being recycled for 50-times, which considerably outperforms the existing membrane photocatalysts. Subsequently, a homemade panel H2O-to-H2 conversion system was fabricated to obtain a 0.05% of solar-to-hydrogen efficiency. In this study, we opens up a prospect for practical application of photocatalysis technology.

Heteroepitaxial Control of Fermi Liquid, Hund Metal, and Mott Insulator Phases in Single-Atomic-Layer Ruthenates

Interfaces between dissimilar correlated oxides can offer devices with versatile functionalities, and great efforts have been made to manipulate interfacial electronic phases. However, realizing such phases is often hampered by the inability to directly access the electronic structure information; most correlated interfacial phenomena appear within a few atomic layers from the interface. Here, atomic-scale epitaxy and photoemission spectroscopy are utilized to realize the interface control of correlated electronic phases in atomic-scale ruthenate-titanate heterostructures. While bulk SrRuO₃ is a ferromagnetic metal, the heterointerfaces exclusively generate three distinct correlated phases in the single-atomic-layer limit. The theoretical analysis reveals that atomic-scale structural proximity effects yield Fermi liquid, Hund metal, and Mott insulator phases in the quantum-confined SrRuO₃ . These results highlight the extensive interfacial tunability of electronic phases, hitherto hidden in the atomically thin correlated heterostructure. Moreover, this experimental platform suggests a way to control interfacial electronic phases of various correlated materials.

Electric Control of 2D Van Hove Singularity in Oxide Ultra-Thin Films

Divergent density of states (DOS) can induce extraordinary phenomena such as significant enhancement of superconductivity and unexpected phase transitions. Moreover, van Hove singularities (VHSs) lead to divergent DOS in 2D systems. Despite recent interest in VHSs, only a few controllable cases have been reported to date. In this work, by utilizing an atomically ultra-thin SrRuO₃ film, the electronic structure of a 2D VHS is investigated with angle-resolved photoemission spectroscopy and transport properties are controlled. By applying electric fields with alkali metal deposition and ionic-liquid gating methods, the 2D VHS and the sign of the charge carrier are precisely controlled. Use of a tunable 2D VHS in an atomically flat oxide film could serve as a new strategy to realize infinite DOS near the Fermi level, thereby allowing efficient tuning of electric properties.

Comparing Thickness and Doping-Induced Effects on the Normal States of Infinite-Layer Electron-Doped Cuprates: Is There Anything to Learn?

We grew Sr_1-xLa_xCuO₂ thin films and SrCuO₂/Sr_0.9La_0.1CuO₂/SrCuO₂ trilayers by reflection high-energy diffraction-calibrated layer-by-layer molecular beam epitaxy, to study their electrical transport properties as a function of the doping and thickness of the central Sr_0.9La_0.1CuO₂ layer. For the trilayer samples, as already observed in underdoped SLCO films, the electrical resistivity versus temperature curves as a function of the central layer thickness show, for thicknesses thinner than 20 unit cells, sudden upturns in the low temperature range with the possibility for identifying, in the normal state, the T* and a T** temperatures, respectively, separating high-temperature linear behavior and low-temperature quadratic dependence. By plotting the T* and T** values as a function of T_C^onset for both the thin films and the trilayers, the data fall on the same curves. This result suggests that, for the investigated trilayers, the superconducting critical temperature is the important parameter able to describe the normal state properties and that, in the limit of very thin central layers, such properties are mainly influenced by the modification of the energy band structure and not by interface-related disorder.