Theoretical model of nickel oxide superconducting matrix

[ Instrument network instrument R & D ] In the nickel oxides LaNiO2 and NdNiO2, Ni is +1 valence, there are 9 electrons in its 3d orbit, and the dx2-y2 orbit is half full. Sr doping will introduce holes, similar to hole doping Copper oxide high temperature superconductors, for many years people have speculated that there may also be high temperature superconductors. Recently, the journal Nature reported a superconducting phase found in Nd1-xSrxNiO2 films, confirming this expectation.

In order to clarify the physical properties of nickel oxide superconductor, Yang Yifeng, researcher of the EX9 group of the Institute of Physics of the Chinese Academy of Sciences / Beijing National Research Center for Condensed Matter Physics, cooperated with Zhang Guangming, a professor at Tsinghua University, and Zhang Fuchun, a professor at the Kavri Institute of Theoretical Sciences, University of Chinese Academy of Sciences. A theoretical model of nickel oxide superconductors. They carefully analyzed the experimental data and found that strong Kondo scattering exists in both the undoped NdNiO2 or LaNiO2 matrix, resulting in a typical logarithmic temperature-dependent behavior of the resistance and Hall coefficient at low temperatures; In Nd1-xSrxNiO2, the resistance exhibits a strange metal behavior similar to that of doped copper oxide above the superconducting transition. Based on the above facts, they proposed that the parent body of the nickel oxide superconductor is a self-doped Mott insulator. Most of the 3dx2-y2 electrons of Ni are relatively local, forming a spin lattice, and a small part is transferred to the 5d orbital of Nd or La. on. These traveling 5d electrons not only introduce holes (holon) on the Ni spin lattice, but also undergo Kondo scattering with these spins and form a Kondo singlet (doublon) at low temperature, resulting in low-energy doublon-holon excitation and destruction. Possible long magnetic programs.

The above work provides a theoretical basis for understanding nickel oxide superconductors, and points out that the system has the dual characteristics of heavy fermions and copper oxides, and is an important object for exploring new physics.