Ternary transition metal chalcogenides provide a rich platform to search and study intriguing electronic properties. Using angle-resolved photoemission spectroscopy and ab initio calculation, we investigate the electr...Ternary transition metal chalcogenides provide a rich platform to search and study intriguing electronic properties. Using angle-resolved photoemission spectroscopy and ab initio calculation, we investigate the electronic structure of Cu_(2)TlX_(2)(X = Se, Te), ternary transition metal chalcogenides with quasi-two-dimensional crystal structure. The band dispersions near the Fermi level are mainly contributed by the Te/Se p orbitals. According to our ab-initio calculation, the electronic structure changes from a semiconductor with indirect band gap in Cu_(2)TlSe_(2) to a semimetal in Cu_(2)TlTe_(2), suggesting a band-gap tunability with the composition of Se and Te. By comparing ARPES experimental data with the calculated results, we identify strong modulation of the band structure by spin–orbit coupling in the compounds. Our results provide a ternary platform to study and engineer the electronic properties of transition metal chalcogenides related to large spin–orbit coupling.展开更多
Sulfite(SO_(3)^(2−))activation is one of the most potential sulfate-radical-based advanced oxidation processes,and the catalysts with high efficiency and low-cost are greatly desired.In this study,the cobalt nanoparti...Sulfite(SO_(3)^(2−))activation is one of the most potential sulfate-radical-based advanced oxidation processes,and the catalysts with high efficiency and low-cost are greatly desired.In this study,the cobalt nanoparticles embedded in nitrogen-doped graphite layers(Co@NC),were used to activate SO32−for removal of Methyl Orange in aqueous solution.The Co@NC catalysts were synthesized via pyrolysis of Co^(2+)-based metal-organic framework(Co-MOF),where CoO was firstly formed at 400℃ and then partially reduced to Co nanoparticles embedded in carbon layers at 800℃.The Co@NC catalysts were more active than other cobaltbased catalysts such as Co^(2+),Co_(3)O_(4) and CoFe_(2)O_(4),due to the synergistic effect of metallic Co and CoxOy.A series of chain reaction between Co species and dissolved oxygen was established,with the production and transformation of SO_(3)•−,SO_(5)^(2−),and subsequent active radicals SO_(4)•−and HO•.In addition,HCO_(3)−was found to play a key role in the reaction by complexing with Co species on the surface of the catalysts.The results provide a new promising strategy by using the Co@NC catalyst for SO3_(2)−oxidation to promote organic pollutants degradation.展开更多
In iron-based superconductors,the(0,π) or(π,0) nematicity,which describes an electronic anisotropy with a fourfold symmetry breaking,is well established and believed to be important for understanding the superconduc...In iron-based superconductors,the(0,π) or(π,0) nematicity,which describes an electronic anisotropy with a fourfold symmetry breaking,is well established and believed to be important for understanding the superconducting mechanism.However,how exactly such a nematic order observed in the normal state can be related to the superconducting pairing is still elusive.Here,by performing angular-dependent in-plane magnetoresistivity using ultra-thin flakes in the steep superconducting transition region,we unveil a nematic superconducting order along the(π,π) direction in electron-doped BaFe_(2-x)Ni_(x)As_(2) from under-doped to heavily overdoped regimes with x=0.065- 0.18.It shows superconducting gap maxima along the(π,π) direction rotated by 45° from the nematicity along(0, π) or(π,0) direction observed in the normal state.A similar(π,π)-type nematicity is also observed in the under-doped and optimally doped hole-type Ba1-yKyFe2 As_(2),with y=0.2-0.5.These results suggest that the(π,π) nematic superconducting order is a universal feature that needs to be taken into account in the superconducting pairing mechanism in iron-based superconductors.展开更多
In this study we successfully intercalated potassium(K) atoms into single ZrTe_5 crystals by liquid ammonia method, and found a semimetal-to-semiconductor transition at low temperatures in K-intercalated ZrTe_5. As th...In this study we successfully intercalated potassium(K) atoms into single ZrTe_5 crystals by liquid ammonia method, and found a semimetal-to-semiconductor transition at low temperatures in K-intercalated ZrTe_5. As the K concentration increased, the resistance anomalous peak was gradually suppressed until finally disappearing. Whilst, the corresponding Hall resistance measurements consistently showed a sign reversal. The semimetal-to-semiconductor transition can be attributed to a lattice expansion induced by atom intercalation, leading to a larger energy band gap.展开更多
In order to obtain high-quality superconducting qubits, we employed a cold-development technique, using temperatures down to-20°C, to fabricate Al/AlOx/Al Josephson junctions. Cold development greatly reduced the...In order to obtain high-quality superconducting qubits, we employed a cold-development technique, using temperatures down to-20°C, to fabricate Al/AlOx/Al Josephson junctions. Cold development greatly reduced the sensitivity of the electron-beam resist to the developer, eliminated molecules of the electron-beam resist at trench edges, and improved the repeatability and reliability of the nanopatterning process. The fabricated samples have well-defined geometries and increased dose margins, with lateral sizes of 100 nm×100 nm on both silicon and sapphire substrates. Together with the bridge-free fabrication method we used in these experiments, we believe that the cold-development technique can play an important role in quantum information technology that employs superconducting qubits.展开更多
We investigated the superconducting properties of Fe_(1+y)Te_(0:6)Se_(0:4) single-crystalline microbridges with a width of 4 m and thicknesses ranging from 20.8 to 136.2 nm. The temperature-dependent in-plane resistan...We investigated the superconducting properties of Fe_(1+y)Te_(0:6)Se_(0:4) single-crystalline microbridges with a width of 4 m and thicknesses ranging from 20.8 to 136.2 nm. The temperature-dependent in-plane resistance of the bridges exhibited a type of metalinsulator transition in the normal state. The critical current density(J_c) of the microbridge with a thickness of 136.2 nm was82.3 kA/cm^2 at 3K and reached 105 kA/cm^2 after extrapolation to T = 0 K. The current versus voltage characteristics of the microbridges showed a Josephson-like behavior with an obvious hysteresis. These results demonstrate the potential application of ultra-thin Fe-based microbridges in superconducting electronic devices such as bolometric detectors.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 11774190)。
文摘Ternary transition metal chalcogenides provide a rich platform to search and study intriguing electronic properties. Using angle-resolved photoemission spectroscopy and ab initio calculation, we investigate the electronic structure of Cu_(2)TlX_(2)(X = Se, Te), ternary transition metal chalcogenides with quasi-two-dimensional crystal structure. The band dispersions near the Fermi level are mainly contributed by the Te/Se p orbitals. According to our ab-initio calculation, the electronic structure changes from a semiconductor with indirect band gap in Cu_(2)TlSe_(2) to a semimetal in Cu_(2)TlTe_(2), suggesting a band-gap tunability with the composition of Se and Te. By comparing ARPES experimental data with the calculated results, we identify strong modulation of the band structure by spin–orbit coupling in the compounds. Our results provide a ternary platform to study and engineer the electronic properties of transition metal chalcogenides related to large spin–orbit coupling.
基金supported by the National Natural Science Foundation of China(No.51978542)Special Project of the Central Committee Guides Local Science and Technology Development of Hubei Province(No.2019ZYYD073)
文摘Sulfite(SO_(3)^(2−))activation is one of the most potential sulfate-radical-based advanced oxidation processes,and the catalysts with high efficiency and low-cost are greatly desired.In this study,the cobalt nanoparticles embedded in nitrogen-doped graphite layers(Co@NC),were used to activate SO32−for removal of Methyl Orange in aqueous solution.The Co@NC catalysts were synthesized via pyrolysis of Co^(2+)-based metal-organic framework(Co-MOF),where CoO was firstly formed at 400℃ and then partially reduced to Co nanoparticles embedded in carbon layers at 800℃.The Co@NC catalysts were more active than other cobaltbased catalysts such as Co^(2+),Co_(3)O_(4) and CoFe_(2)O_(4),due to the synergistic effect of metallic Co and CoxOy.A series of chain reaction between Co species and dissolved oxygen was established,with the production and transformation of SO_(3)•−,SO_(5)^(2−),and subsequent active radicals SO_(4)•−and HO•.In addition,HCO_(3)−was found to play a key role in the reaction by complexing with Co species on the surface of the catalysts.The results provide a new promising strategy by using the Co@NC catalyst for SO3_(2)−oxidation to promote organic pollutants degradation.
基金Supported by the National Natural Science Foundation of China(Grant Nos.61771234,61727805,11674157,11674158,11774152,11822405,61521001,6157121961501222)+6 种基金the National Key Projects for Research and Development of China(Grant Nos.2016YFA0300401,2017YFB0503302,2017YFA03040022017YFB0503300)the start-up funding from ShanghaiTech University,Innovative Research Team in University(PCSIRT)the Natural Science Foundation of Shanghai Municipality(Grant No.20ZR1436100)the Science and Technology Commission of Shanghai Municipality(Grant No.YDZX20203100001438)Jiangsu Key Laboratory of Advanced Techniques for Manipulating Electromagnetic Waves,Natural Science Foundation of Jiangsu Province(Grant No.BK20180006)the Fundamental Research Funds for the Central Universities(Grant No.020414380117)。
文摘In iron-based superconductors,the(0,π) or(π,0) nematicity,which describes an electronic anisotropy with a fourfold symmetry breaking,is well established and believed to be important for understanding the superconducting mechanism.However,how exactly such a nematic order observed in the normal state can be related to the superconducting pairing is still elusive.Here,by performing angular-dependent in-plane magnetoresistivity using ultra-thin flakes in the steep superconducting transition region,we unveil a nematic superconducting order along the(π,π) direction in electron-doped BaFe_(2-x)Ni_(x)As_(2) from under-doped to heavily overdoped regimes with x=0.065- 0.18.It shows superconducting gap maxima along the(π,π) direction rotated by 45° from the nematicity along(0, π) or(π,0) direction observed in the normal state.A similar(π,π)-type nematicity is also observed in the under-doped and optimally doped hole-type Ba1-yKyFe2 As_(2),with y=0.2-0.5.These results suggest that the(π,π) nematic superconducting order is a universal feature that needs to be taken into account in the superconducting pairing mechanism in iron-based superconductors.
基金supported by the Ministry of Science and Technology of China(Grant Nos.2014CB921103,and 2015CB921203)the National Natural Science Foundation of China(Grant Nos.11774149,11790311,11674157,11674154,51032003,1171101156,11374149,and 11374140)
文摘In this study we successfully intercalated potassium(K) atoms into single ZrTe_5 crystals by liquid ammonia method, and found a semimetal-to-semiconductor transition at low temperatures in K-intercalated ZrTe_5. As the K concentration increased, the resistance anomalous peak was gradually suppressed until finally disappearing. Whilst, the corresponding Hall resistance measurements consistently showed a sign reversal. The semimetal-to-semiconductor transition can be attributed to a lattice expansion induced by atom intercalation, leading to a larger energy band gap.
基金supported by the National Natural Science Foundation of China(Grant Nos.61727805,61771234,61501220,61611130069,and61521001)the National Key Research and Devlopment Programme of China(Grant No.2016YFA0301802)+2 种基金Jiangsu Provincial Natural Science Fund(Grant Nos.BK20150561,and BK20160635)the Fundamental Research Funds for the Central UniversitiesNanjing University Innovation and Creative Program for PhD Candidate(Grant No.CXCY17-15)
文摘In order to obtain high-quality superconducting qubits, we employed a cold-development technique, using temperatures down to-20°C, to fabricate Al/AlOx/Al Josephson junctions. Cold development greatly reduced the sensitivity of the electron-beam resist to the developer, eliminated molecules of the electron-beam resist at trench edges, and improved the repeatability and reliability of the nanopatterning process. The fabricated samples have well-defined geometries and increased dose margins, with lateral sizes of 100 nm×100 nm on both silicon and sapphire substrates. Together with the bridge-free fabrication method we used in these experiments, we believe that the cold-development technique can play an important role in quantum information technology that employs superconducting qubits.
基金supported by the National Natural Science Foundation of China(Grant Nos.11234006,61501220,U1432135,11674054,and 11611140101)Jiangsu Provincial Natural Science Fund(Grant No.SBK2015040804)Opening Project of Wuhan National High Magnetic Field Center(Grant No.2015KF19)
文摘We investigated the superconducting properties of Fe_(1+y)Te_(0:6)Se_(0:4) single-crystalline microbridges with a width of 4 m and thicknesses ranging from 20.8 to 136.2 nm. The temperature-dependent in-plane resistance of the bridges exhibited a type of metalinsulator transition in the normal state. The critical current density(J_c) of the microbridge with a thickness of 136.2 nm was82.3 kA/cm^2 at 3K and reached 105 kA/cm^2 after extrapolation to T = 0 K. The current versus voltage characteristics of the microbridges showed a Josephson-like behavior with an obvious hysteresis. These results demonstrate the potential application of ultra-thin Fe-based microbridges in superconducting electronic devices such as bolometric detectors.
