The nickel-based superconductivity provides a fascinating new platform to explore high-Tc superconductivity.As the infinite-layer nickelates are obtained by removing the apical oxygens from the precursor perovskite ph...The nickel-based superconductivity provides a fascinating new platform to explore high-Tc superconductivity.As the infinite-layer nickelates are obtained by removing the apical oxygens from the precursor perovskite phase,the crystalline quality of the perovskite phase is crucial in synthesizing high quality superconducting nickelates.Especially,cation-related defects,such as the Ruddlesden–Popper-type(RP-type)faults,are unlikely to disappear after the topotactic reduction process and should be avoided during the growth of the perovskite phase.Herein,using reactive molecular beam epitaxy,we report the atomic-scale engineering of the interface structure and demonstrate its impact in reducing crystalline defects in Nd-based nickelate/SrTiO_(3) heterostructures.A simultaneous deposition of stoichiometric Nd and Ni directly on SrTiO_(3) substrates results in prominent Nd vacancies and Ti diffusion at the interface and RP-type defects in nickelate films.In contrast,inserting an extra[NdO]monolayer before the simultaneous deposition of Nd and Ni forms a sharp interface and greatly eliminates RP-type defects in nickelate films.A possible explanation related to the polar discontinuity is also discussed.Our results provide an effective method to synthesize high-quality precursor perovskite phase for the investigation of the novel superconductivity in nickelates.展开更多
The newly discovered superconductivity in infinite-layer nickelate superconducting films has attracted much attention,largely because their crystalline and electronic structures are similar to those of high-T_(c) cupr...The newly discovered superconductivity in infinite-layer nickelate superconducting films has attracted much attention,largely because their crystalline and electronic structures are similar to those of high-T_(c) cuprate superconductors.The upper critical field can provide a great deal of information on the subject of superconductivity,but detailed experimental data are still lacking for these films.We present the temperature-and angle-dependence of resistivity,measured under different magnetic fields H in Nd_(0.8)Sr_(0.2)NiO_(2) thin films.The onset superconducting transition occurs at about 16.2 K at 0 T.Temperature-dependent upper critical fields,determined using a criterion very close to the onset transition,show a clear negative curvature near the critical transition temperature,which can be explained as a consequence of the paramagnetically limited effect on superconductivity.The temperaturedependent anisotropy of the upper critical field is obtained from resistivity data,which yields a value decreasing from 3 to 1.2 with a reduction in temperature.This can be explained in terms of the variable contribution from the orbital limit effect on the upper critical field.The angle-dependence of resistivity at a fixed temperature,and at different magnetic fields,cannot be scaled to a curve,which deviates from the prediction of the anisotropic Ginzburg-Landau theory.However,at low temperatures,the resistance difference can be scaled via the parameter H^(β)| cos θ|(β=6-1),with θ being the angle enclosed between the c-axis and the applied magnetic field.As the first detailed study of the upper critical field of nickelate thin films,our results clearly indicate a small anisotropy,and a paramagnetically limited effect,in terms of superconductivity,in nickelate superconductors.展开更多
基金supported by the National Key Projects for Research and Development of China(Grant No.2022YFA1402502 and 2021YFA1400400)the National Natural Science Foundation of China(Grant No.11861161004)+2 种基金the Fundamental Research Funds for the Central Universities(Grant No.0213–14380221)the Research Grants Council of Hong Kong(Grant No.N PolyU531/18)the Hong Kong Polytechnic University(Grant No.ZVRP)。
文摘The nickel-based superconductivity provides a fascinating new platform to explore high-Tc superconductivity.As the infinite-layer nickelates are obtained by removing the apical oxygens from the precursor perovskite phase,the crystalline quality of the perovskite phase is crucial in synthesizing high quality superconducting nickelates.Especially,cation-related defects,such as the Ruddlesden–Popper-type(RP-type)faults,are unlikely to disappear after the topotactic reduction process and should be avoided during the growth of the perovskite phase.Herein,using reactive molecular beam epitaxy,we report the atomic-scale engineering of the interface structure and demonstrate its impact in reducing crystalline defects in Nd-based nickelate/SrTiO_(3) heterostructures.A simultaneous deposition of stoichiometric Nd and Ni directly on SrTiO_(3) substrates results in prominent Nd vacancies and Ti diffusion at the interface and RP-type defects in nickelate films.In contrast,inserting an extra[NdO]monolayer before the simultaneous deposition of Nd and Ni forms a sharp interface and greatly eliminates RP-type defects in nickelate films.A possible explanation related to the polar discontinuity is also discussed.Our results provide an effective method to synthesize high-quality precursor perovskite phase for the investigation of the novel superconductivity in nickelates.
基金the National Key R&D Program of China(Grant Nos.2016YFA0300401 and 2018YFA0704202)the National Natural Science Foundation of China(Grant Nos.12061131001,11774153,and 1861161004)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB25000000)the Fundamental Research Funds for the Central Universities(Grant No.0213-14380167)。
文摘The newly discovered superconductivity in infinite-layer nickelate superconducting films has attracted much attention,largely because their crystalline and electronic structures are similar to those of high-T_(c) cuprate superconductors.The upper critical field can provide a great deal of information on the subject of superconductivity,but detailed experimental data are still lacking for these films.We present the temperature-and angle-dependence of resistivity,measured under different magnetic fields H in Nd_(0.8)Sr_(0.2)NiO_(2) thin films.The onset superconducting transition occurs at about 16.2 K at 0 T.Temperature-dependent upper critical fields,determined using a criterion very close to the onset transition,show a clear negative curvature near the critical transition temperature,which can be explained as a consequence of the paramagnetically limited effect on superconductivity.The temperaturedependent anisotropy of the upper critical field is obtained from resistivity data,which yields a value decreasing from 3 to 1.2 with a reduction in temperature.This can be explained in terms of the variable contribution from the orbital limit effect on the upper critical field.The angle-dependence of resistivity at a fixed temperature,and at different magnetic fields,cannot be scaled to a curve,which deviates from the prediction of the anisotropic Ginzburg-Landau theory.However,at low temperatures,the resistance difference can be scaled via the parameter H^(β)| cos θ|(β=6-1),with θ being the angle enclosed between the c-axis and the applied magnetic field.As the first detailed study of the upper critical field of nickelate thin films,our results clearly indicate a small anisotropy,and a paramagnetically limited effect,in terms of superconductivity,in nickelate superconductors.
