The recent discovery of ambient-pressure superconductivity with a critical temperature Tc exceeding 40 K in La_(3)Ni_(2)O_(7) thin films represents a significant advancement in the field of nickelate superconductivity...The recent discovery of ambient-pressure superconductivity with a critical temperature Tc exceeding 40 K in La_(3)Ni_(2)O_(7) thin films represents a significant advancement in the field of nickelate superconductivity.Motivated by recent experimental reports,we investigate an 11-band d–p Hubbard model with tight-binding parameters derived from ab initio calculations,employing large-scale determinant quantum Monte Carlo and cellular dynamical mean-field theory.Our results show that the dominant superexchange couplings in the La_(3)Ni_(2)O_(7) thin films are substantially weaker than those in the bulk material at 29.5 GPa.Specifically,the out-of-plane antiferromagnetic correlation between the Ni-d_(3z^(2)–r^(2)) orbitals is reduced by approximately 27%in the film,whereas the in-plane magnetic correlations remain largely unaffected.We further evaluate the corresponding antiferromagnetic coupling constants,J_(⊥) and J_(||),within a perturbative framework.Regarding charge-transfer properties,we find that biaxial compressive strain in the films reduces the charge-transfer gap.We further resolve the orbital distribution of doped holes and electrons between the IP(Ni-d_(x^(2)–y^(2)) and O-p_(x)/p_(y))and OP(Ni-d_(3z^(2)–r^(2)) and O-p_(z))orbitals,revealing a pronounced particle–hole asymmetry.These findings lay the groundwork for constructing a low-energy t–J model for La_(3)Ni_(2)O_(7) films and provide key insights into the physical distinctions between thin-film and bulk bilayer nickelates.展开更多
Superconducting elect rides have attracted growing attention for their potential to achieve high superconducting transition temperatures(T_(C))under pressure.However,many known elect rides are chemically reactive and ...Superconducting elect rides have attracted growing attention for their potential to achieve high superconducting transition temperatures(T_(C))under pressure.However,many known elect rides are chemically reactive and unstable,making high-quality single-crystal growth,characterization,and measurements difficult,and most do not exhibit superconductivity at ambient pressure.In contrast,La_(3) In stands out for its ambient-pressure superconductivity(T_(C)∼9.4 K)and the availability of high-quality single crystals.Here,we investigate its low-energy electronic structure using angle-resolved photoemission spectroscopy and first-principles calculations.The bands near the Fermi energy(E_(F))are mainly derived from La 5d and In 5p orbitals.A saddle point is directly observed at the Brillouin zone(BZ)boundary,while a three-dimensional Van Hove singularity crosses E_(F) at the BZ corner.First-principles calculations further reveal topological Dirac surface states within the bulk energy gap above E_(F).The coexistence of a high density of states and in-gap topological surface states near𝐸F suggests that La3In offers a promising platform for tuning superconductivity and exploring possible topological superconducting phases through doping or external pressure.展开更多
研究了190~230℃低温退火对拉拔态Al-0.3La合金单丝微观组织、抗拉强度和导电率的影响。结果表明,拉拔后合金单丝的铝晶粒呈纤维状分布,平均晶粒尺寸为2.11μm,并且在基体上分布有微米级Al Fe Si La颗粒以及纳米Al Fe Si颗粒。随着退火...研究了190~230℃低温退火对拉拔态Al-0.3La合金单丝微观组织、抗拉强度和导电率的影响。结果表明,拉拔后合金单丝的铝晶粒呈纤维状分布,平均晶粒尺寸为2.11μm,并且在基体上分布有微米级Al Fe Si La颗粒以及纳米Al Fe Si颗粒。随着退火温度升高,Al Fe Si La颗粒中的La含量逐渐增加,铝基体再结晶程度加快,晶粒择优取向逐渐不明显,同时铝晶粒尺寸增加,位错密度和小角度晶界占比下降。当退火温度增加到230℃时,合金的抗拉强度由194.18 MPa降低到158.35 MPa,导电率由60.9%IACS增加到61.7%IACS。强度的降低主要由形变强化、细晶强化和固溶强化作用减弱导致;而随退火温度升高,基体中固溶La含量的下降,以及晶界数量和位错密度减小是造成合金导电率增加的主要原因。展开更多
It is crucial to develop arsenic removal adsorbents with strong sulfur resistance under middle-low-temperature flue gas conditions(<400℃).In this work,five Fe-Ce-La oxides were prepared by co-precipitation method,...It is crucial to develop arsenic removal adsorbents with strong sulfur resistance under middle-low-temperature flue gas conditions(<400℃).In this work,five Fe-Ce-La oxides were prepared by co-precipitation method,and FeCeLaO/SiO_(2)-Al_(2)O_(3) composite adsorbents were prepared by coupling fly ash-based Si-Al carriers.The active components Fe-Ce-La oxides and Si-Al carriers were characterized by TPD,TG,XRF,BET and XPS,respectively.The effects of temperature,Si/Al ratio and FeCeLaO loading rate on the sulfur resistance were investigated.Results show that the SO_(2) promotes the arsenic removal of Fe_(2)O_(3),CeLaO and FeCeLaO.At 400℃,the arsenic removal efficiencies of the three oxides increase from 45.3%,72.5% and 81.3% without SO_(2) to 62.6%,80.5%and 91.0%,respectively.The SO_(2) inhibits the arsenic removal of La_(2)O_(2)CO_(3) and FeLaO,and the inhibition effect is pronounced at high temperatures.The sulfur poisoning resistance of Si-Al carriers increases with the increase of Si/Al ratio.When the Si/Al ratio is increased to 9.74,the arsenic removal efficiency in the SO_(2) environment is 13.9% higher than that in the absence of SO_(2).Introducing FeCeLaO active components is beneficial for enhancing the SO_(2) poisoning resistance of Si-Al carriers.The strong sulfur resistance of the FeCeLaO/SiO_(2)-Al_(2)O_(3) composite adsorbent results from multiple factors:protective effects of Ce on Fe,La and Al;sulfation-induced generation of Ce^(3+)and surface-adsorbed oxygen;and strong surface acidity of SiO_(2).展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.12494591,12494594,and 92565303)the National Key R&D Program of China (Grant No.2022YFA1402802)+2 种基金the Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices (Grant No.2022B1212010008)the Research Center for Magnetoelectric Physics of Guangdong Province (Grant No.2024B0303390001)the Guangdong Provincial Quantum Science Strategic Initiative (Grant No.GDZX2401010)。
文摘The recent discovery of ambient-pressure superconductivity with a critical temperature Tc exceeding 40 K in La_(3)Ni_(2)O_(7) thin films represents a significant advancement in the field of nickelate superconductivity.Motivated by recent experimental reports,we investigate an 11-band d–p Hubbard model with tight-binding parameters derived from ab initio calculations,employing large-scale determinant quantum Monte Carlo and cellular dynamical mean-field theory.Our results show that the dominant superexchange couplings in the La_(3)Ni_(2)O_(7) thin films are substantially weaker than those in the bulk material at 29.5 GPa.Specifically,the out-of-plane antiferromagnetic correlation between the Ni-d_(3z^(2)–r^(2)) orbitals is reduced by approximately 27%in the film,whereas the in-plane magnetic correlations remain largely unaffected.We further evaluate the corresponding antiferromagnetic coupling constants,J_(⊥) and J_(||),within a perturbative framework.Regarding charge-transfer properties,we find that biaxial compressive strain in the films reduces the charge-transfer gap.We further resolve the orbital distribution of doped holes and electrons between the IP(Ni-d_(x^(2)–y^(2)) and O-p_(x)/p_(y))and OP(Ni-d_(3z^(2)–r^(2)) and O-p_(z))orbitals,revealing a pronounced particle–hole asymmetry.These findings lay the groundwork for constructing a low-energy t–J model for La_(3)Ni_(2)O_(7) films and provide key insights into the physical distinctions between thin-film and bulk bilayer nickelates.
基金supported by the National Natural Science Foundation of China(Grant Nos.12222413,12174443,12274459,and 12404266)the National Key R&D Program of China(Grant Nos.2023YFA1406500,2022YFA1403800,and 2022YFA1403103)+3 种基金the Natural Science Foundation of Shanghai (Grant No.23ZR1482200)the Natural Science Foundation of Ningbo (Grant No.2024J019)the Science Research Project of Hebei Education Department (Grant No.BJ2025060)the funding of Ningbo Yongjiang Talent Program。
文摘Superconducting elect rides have attracted growing attention for their potential to achieve high superconducting transition temperatures(T_(C))under pressure.However,many known elect rides are chemically reactive and unstable,making high-quality single-crystal growth,characterization,and measurements difficult,and most do not exhibit superconductivity at ambient pressure.In contrast,La_(3) In stands out for its ambient-pressure superconductivity(T_(C)∼9.4 K)and the availability of high-quality single crystals.Here,we investigate its low-energy electronic structure using angle-resolved photoemission spectroscopy and first-principles calculations.The bands near the Fermi energy(E_(F))are mainly derived from La 5d and In 5p orbitals.A saddle point is directly observed at the Brillouin zone(BZ)boundary,while a three-dimensional Van Hove singularity crosses E_(F) at the BZ corner.First-principles calculations further reveal topological Dirac surface states within the bulk energy gap above E_(F).The coexistence of a high density of states and in-gap topological surface states near𝐸F suggests that La3In offers a promising platform for tuning superconductivity and exploring possible topological superconducting phases through doping or external pressure.
文摘研究了190~230℃低温退火对拉拔态Al-0.3La合金单丝微观组织、抗拉强度和导电率的影响。结果表明,拉拔后合金单丝的铝晶粒呈纤维状分布,平均晶粒尺寸为2.11μm,并且在基体上分布有微米级Al Fe Si La颗粒以及纳米Al Fe Si颗粒。随着退火温度升高,Al Fe Si La颗粒中的La含量逐渐增加,铝基体再结晶程度加快,晶粒择优取向逐渐不明显,同时铝晶粒尺寸增加,位错密度和小角度晶界占比下降。当退火温度增加到230℃时,合金的抗拉强度由194.18 MPa降低到158.35 MPa,导电率由60.9%IACS增加到61.7%IACS。强度的降低主要由形变强化、细晶强化和固溶强化作用减弱导致;而随退火温度升高,基体中固溶La含量的下降,以及晶界数量和位错密度减小是造成合金导电率增加的主要原因。
文摘It is crucial to develop arsenic removal adsorbents with strong sulfur resistance under middle-low-temperature flue gas conditions(<400℃).In this work,five Fe-Ce-La oxides were prepared by co-precipitation method,and FeCeLaO/SiO_(2)-Al_(2)O_(3) composite adsorbents were prepared by coupling fly ash-based Si-Al carriers.The active components Fe-Ce-La oxides and Si-Al carriers were characterized by TPD,TG,XRF,BET and XPS,respectively.The effects of temperature,Si/Al ratio and FeCeLaO loading rate on the sulfur resistance were investigated.Results show that the SO_(2) promotes the arsenic removal of Fe_(2)O_(3),CeLaO and FeCeLaO.At 400℃,the arsenic removal efficiencies of the three oxides increase from 45.3%,72.5% and 81.3% without SO_(2) to 62.6%,80.5%and 91.0%,respectively.The SO_(2) inhibits the arsenic removal of La_(2)O_(2)CO_(3) and FeLaO,and the inhibition effect is pronounced at high temperatures.The sulfur poisoning resistance of Si-Al carriers increases with the increase of Si/Al ratio.When the Si/Al ratio is increased to 9.74,the arsenic removal efficiency in the SO_(2) environment is 13.9% higher than that in the absence of SO_(2).Introducing FeCeLaO active components is beneficial for enhancing the SO_(2) poisoning resistance of Si-Al carriers.The strong sulfur resistance of the FeCeLaO/SiO_(2)-Al_(2)O_(3) composite adsorbent results from multiple factors:protective effects of Ce on Fe,La and Al;sulfation-induced generation of Ce^(3+)and surface-adsorbed oxygen;and strong surface acidity of SiO_(2).
