Schwertmannite is an amorphous iron(III)-oxyhydroxysulfate that forms in acid mine drainage(AMD) environments. The characteristic of high heavy metal adsorption capability makes schwertmannite a potentially useful, en...Schwertmannite is an amorphous iron(III)-oxyhydroxysulfate that forms in acid mine drainage(AMD) environments. The characteristic of high heavy metal adsorption capability makes schwertmannite a potentially useful, environmentally friendly material in wastewater treatment. Unstable schwertmannite is prone to recrystallization.Understanding the mechanisms that induce schwertmannite labilization and affect its capacity to remove heavy metals are of great environmental and geochemical significance.Thiocyanate(SCNˉ) is a hazardous pseudohalide that is also normally found in AMD.However, little is known about the impact of Fe(III)-binding ligand SCNˉ on schwertmannite stability and its subsequent capacity to bind trace elements. Here, we investigated the adsorption of SCNˉ on schwertmannite and subsequent mineral transformation to characterize this little-known process. The appearance of Fe2+indicated that the interactions between schwertmannite and SCNˉ may involve complexation and reduction reactions. Results showed that the majority of the adsorbed-SCNˉ was immobilized on schwertmannite during the 60-days transformation. The transformation rates of schwertmannite increased with increasing concentrations of SCNˉ. Goethite was detected as the dominant transformation product with or without SCNˉ. The mechanisms of SCNˉ-promoted dissolution of schwertmannite can be described as follows:(1) formation of Fe(III)–NCS complexes on the schwertmannite surface and in solution, a process which increases the reactivity of solid phase Fe(III);(2) the extraction of Fe(III) from schwertmannite by SCNˉ and subsequent schwertmannite dissolution; and(3) the formation of secondary minerals from extracted Fe(III). These findings may improve AMD treatment strategies and provide insight into the use and potential reuse of schwertmannite as a trace element sorbent.展开更多
The discovery of high temperature superconductivity in single unit cell(UC)FeSe on TiO2-δterminated perovskite SrTiO3(001)substrates[1]has attracted intensive attention on searching for new superconducting systems wi...The discovery of high temperature superconductivity in single unit cell(UC)FeSe on TiO2-δterminated perovskite SrTiO3(001)substrates[1]has attracted intensive attention on searching for new superconducting systems with engineered interfaces as well as understanding the mechanism of interface high temperature superconductivity.展开更多
Atomic characterization on tetragonal FeAs layer and engineering FeAs superlattices is highly desirable to get deep insight into the multi-band superconductivity in iron-pnictides.We fabricate the tetragonal FeAs laye...Atomic characterization on tetragonal FeAs layer and engineering FeAs superlattices is highly desirable to get deep insight into the multi-band superconductivity in iron-pnictides.We fabricate the tetragonal FeAs layer by topotactic reaction of FeTe films with arsenic and then obtain KxFe_(2)As_(2)upon potassium intercalation using molecular beam epitaxy.The in-situ low-temperature√2×√2scanning tunneling microscopy/spectroscopy investigations demonstrate characteristic reconstruction of the FeAs layer and stripe pattern of KxFe_(2)As_(2),accompanied by the development of a superconducting-like gap.The ex-situ transport measurement with FeTe capping layers shows a superconducting transition with an onset temperature of 10 K.This work provides a promising way to characterize the FeAs layer directly and explore rich emergent physics with epitaxial superlattice design.展开更多
Spatially uniform high-temperature superconducting films are highly desirable for exploring novel properties and popularizing applications.To improve the uniformity,we fabricate monolayer FeSexTe1−x(0<x≤1)films on...Spatially uniform high-temperature superconducting films are highly desirable for exploring novel properties and popularizing applications.To improve the uniformity,we fabricate monolayer FeSexTe1−x(0<x≤1)films on SrTiO3(001)by topotactic reaction of monolayer FeTe films with selenium.Using in situ low-temperature scanning tunneling microscopy/spectroscopy,we demonstrate atomic-level uniformity of element distribution and well-defined superconducting gaps of~15 meV in FeSexTe1−x films.In particular,the monolayer FeSe films exhibit fewer line defects and higher superfluid density as evidenced by sharper coherence peaks than those prepared by the co-evaporation method.Our results provide a promising way to optimize sample quality and lay a foundation for studying new physics and drawing reliable conclusions.展开更多
Nickelates represent an emerging class of superconductors that demand innovative approaches for structural and electronic phase modulations.Continuous control over superconductor-insulator transition(SIT)in nickelates...Nickelates represent an emerging class of superconductors that demand innovative approaches for structural and electronic phase modulations.Continuous control over superconductor-insulator transition(SIT)in nickelates remains challenging,hindering both fundamental understanding and potential applications.Here,we demonstrate SIT in infinite-layer nickelate superconductors utilizing multiple techniques,including an operando monitored reduction(OMR)method.OMR enables ultrawide-range continuous modulation of the Ni 3d orbital electron occupancy from∼3d^(7)to∼3d^(9).The 3d occupancy is calibrated through systematic synchrotron X-ray absorption(XAS),combined with scanning transmission electron microscopy(STEM)annular bright field(ABF)analysis of oxygen atoms.SIT is further modulated via ionic liquid gating and magnetic field.Strikingly different from cuprates,our Nernst effect measurements show that pairing initiates at the onset of the resistive drop.The subsequent emergence of the Meissner effect at zero resistance marks the establishment of global phase coherence.Angle-dependent magnetotransport within the transition temperature regime indicates a mixture of two-dimensional(2D)and three-dimensional(3D)superconducting characters,suggesting the observed SIT deviates from the canonical 2D model.Our results provide a unique perspective on the interplay of structural and electronic phase transitions in the infinite-layer nickelates across the oxygen content-magnetic field-temperature parameter space.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 41330639 and 41720104004)the National Key Research and Development Program of China (No. 2017YFD0801000)
文摘Schwertmannite is an amorphous iron(III)-oxyhydroxysulfate that forms in acid mine drainage(AMD) environments. The characteristic of high heavy metal adsorption capability makes schwertmannite a potentially useful, environmentally friendly material in wastewater treatment. Unstable schwertmannite is prone to recrystallization.Understanding the mechanisms that induce schwertmannite labilization and affect its capacity to remove heavy metals are of great environmental and geochemical significance.Thiocyanate(SCNˉ) is a hazardous pseudohalide that is also normally found in AMD.However, little is known about the impact of Fe(III)-binding ligand SCNˉ on schwertmannite stability and its subsequent capacity to bind trace elements. Here, we investigated the adsorption of SCNˉ on schwertmannite and subsequent mineral transformation to characterize this little-known process. The appearance of Fe2+indicated that the interactions between schwertmannite and SCNˉ may involve complexation and reduction reactions. Results showed that the majority of the adsorbed-SCNˉ was immobilized on schwertmannite during the 60-days transformation. The transformation rates of schwertmannite increased with increasing concentrations of SCNˉ. Goethite was detected as the dominant transformation product with or without SCNˉ. The mechanisms of SCNˉ-promoted dissolution of schwertmannite can be described as follows:(1) formation of Fe(III)–NCS complexes on the schwertmannite surface and in solution, a process which increases the reactivity of solid phase Fe(III);(2) the extraction of Fe(III) from schwertmannite by SCNˉ and subsequent schwertmannite dissolution; and(3) the formation of secondary minerals from extracted Fe(III). These findings may improve AMD treatment strategies and provide insight into the use and potential reuse of schwertmannite as a trace element sorbent.
基金supported by the National Natural Science Foundation of China (11574174, 11774193, 11790311, 11404183, 51522212, 51421002, and 51672307)the National Basic Research Program of China (2015CB921000 and 2014CB921002)the Strategic Priority Research Program of Chinese Academy of Sciences (XDB07030200)
文摘The discovery of high temperature superconductivity in single unit cell(UC)FeSe on TiO2-δterminated perovskite SrTiO3(001)substrates[1]has attracted intensive attention on searching for new superconducting systems with engineered interfaces as well as understanding the mechanism of interface high temperature superconductivity.
基金supported by the National Natural Science Foundation of China(Nos.12074210,51788104,11790311,and 12141403)the Basic and Applied Basic Research Major Programme of Guangdong Province of China(No.2021B0301030003)Jihua Laboratory(Project No.X210141TL210).
文摘Atomic characterization on tetragonal FeAs layer and engineering FeAs superlattices is highly desirable to get deep insight into the multi-band superconductivity in iron-pnictides.We fabricate the tetragonal FeAs layer by topotactic reaction of FeTe films with arsenic and then obtain KxFe_(2)As_(2)upon potassium intercalation using molecular beam epitaxy.The in-situ low-temperature√2×√2scanning tunneling microscopy/spectroscopy investigations demonstrate characteristic reconstruction of the FeAs layer and stripe pattern of KxFe_(2)As_(2),accompanied by the development of a superconducting-like gap.The ex-situ transport measurement with FeTe capping layers shows a superconducting transition with an onset temperature of 10 K.This work provides a promising way to characterize the FeAs layer directly and explore rich emergent physics with epitaxial superlattice design.
基金This work was supported by the National Natural Science Foundation of China(Nos.12074210,51788104 and 11790311)the National Basic Research Program of China(Nos.2017YFA0303303)+1 种基金the Basic and Applied Basic Research Major Programme of Guangdong Province,China(No.2021B0301030003)Jihua Laboratory(No.X210141TL210).
文摘Spatially uniform high-temperature superconducting films are highly desirable for exploring novel properties and popularizing applications.To improve the uniformity,we fabricate monolayer FeSexTe1−x(0<x≤1)films on SrTiO3(001)by topotactic reaction of monolayer FeTe films with selenium.Using in situ low-temperature scanning tunneling microscopy/spectroscopy,we demonstrate atomic-level uniformity of element distribution and well-defined superconducting gaps of~15 meV in FeSexTe1−x films.In particular,the monolayer FeSe films exhibit fewer line defects and higher superfluid density as evidenced by sharper coherence peaks than those prepared by the co-evaporation method.Our results provide a promising way to optimize sample quality and lay a foundation for studying new physics and drawing reliable conclusions.
基金supported by the National Key R&D Program of China(2024YFA1408100 and 2022YFA1403101)the National Natural Science Foundation of China(92565303,92265112,12374455,52388201,12504161,12504166,12174325,12404157,92365203,and U24A6002)+9 种基金the Guangdong Major Project of Basic Research(2025B0303000004)the Guangdong Provincial Quantum Science Strategic Initiative(GDZX2501001,GDZX2401004,and GDZX2201001)the Shenzhen Science and Technology Program(KQTD20240729102026004)the Shenzhen Municipal Funding Co-Construction Program Project(SZZX2301004 and SZZX2401001)the China Postdoctoral Science Foundation(2024M761276)the Guangdong Basic and Applied Basic Research Grant(2023A1515011352)the Research Grants Council(RGC)of the Hong Kong Special Administrative Region,China(CityU 21301221,CityU 11309622,CityU 11300923,and CityU 11313325)the Quantum Science and Technology-National Science and Technology Major Project(2021zD0302502)the Natural Science Foundation of Jiangsu Province(BK20253012,BK20243011,and BK20233001)the Open Research Fund Program of Laboratory of Solid State Microstructures,Nanjing University(M38040)。
文摘Nickelates represent an emerging class of superconductors that demand innovative approaches for structural and electronic phase modulations.Continuous control over superconductor-insulator transition(SIT)in nickelates remains challenging,hindering both fundamental understanding and potential applications.Here,we demonstrate SIT in infinite-layer nickelate superconductors utilizing multiple techniques,including an operando monitored reduction(OMR)method.OMR enables ultrawide-range continuous modulation of the Ni 3d orbital electron occupancy from∼3d^(7)to∼3d^(9).The 3d occupancy is calibrated through systematic synchrotron X-ray absorption(XAS),combined with scanning transmission electron microscopy(STEM)annular bright field(ABF)analysis of oxygen atoms.SIT is further modulated via ionic liquid gating and magnetic field.Strikingly different from cuprates,our Nernst effect measurements show that pairing initiates at the onset of the resistive drop.The subsequent emergence of the Meissner effect at zero resistance marks the establishment of global phase coherence.Angle-dependent magnetotransport within the transition temperature regime indicates a mixture of two-dimensional(2D)and three-dimensional(3D)superconducting characters,suggesting the observed SIT deviates from the canonical 2D model.Our results provide a unique perspective on the interplay of structural and electronic phase transitions in the infinite-layer nickelates across the oxygen content-magnetic field-temperature parameter space.
