Theoretical investigation of superconductivity in trilayer square-planar nickelates

Abstract

The discovery of superconductivity in Sr-doped NdNiO2 is a crucial breakthrough in the long pursuit for nickel oxide materials with electronic and magnetic properties similar to those of the cuprates. NdNiO2 is the infinite-layer member of a family of square-planar nickelates with general chemical formula Rn+1NinO2n+2 (R = La, Pr, Nd, n = 2, 3, ...∞). In this letter, we investigate superconductivity in the trilayer member of this series (R4Ni3O8) using a combination of first-principles and t − J model calculations. R4Ni3O8 compounds resemble cuprates more than RNiO2 materials in that only Ni-d x 2 −y 2 bands cross the Fermi level, they exhibit a largely reduced charge transfer energy, and as a consequence superexchange interactions are significantly enhanced. We find that the superconducting instability in doped R4Ni3O8 compounds is considerably stronger with a maximum gap about four times larger than that in Sr0.2Nd0.8NiO2.

Contrasting physical properties of the trilayer nickelates Nd4Ni3O10 and Nd4Ni3O8

“…As for the origin of intrinsic insulating behavior in Nd438, it remains unclear yet. The band structure calculations indicate that the material should be a metal [12], but the insulating behavior may be attributed to the possible buckling of the NiO2 squareplanar or a hidden antiferromagnetic order inducing bandgap opening at the Fermi level, similar to the case in La4Ni3O8 [39,51]. Moreover, the robust insulating behavior may also be caused by the topotactic intercalation of hydrogen in Nd438, in which the phase of Nd4Ni3O8Hx may be formed during the CaH2 reduction reaction.…”

“…Theoretical and experimental efforts have been done to search superconductivity in those materials, such as mixed-valent Ni 1+ /Ni 2+ nickelates and LaNiO3/LaMO3 heterostructures [6,7]. Recently, the observation of superconductivity in Sr-doped NdNiO2 films have been reported [8] and many theoretical works have followed up on this issue [9][10][11][12][13][14][15]. Although the observation of superconductivity in bulk samples is still lacking up to now [16], the related investigation on layered nickelates, especially on 000000-2 the materials containing Ni 1+ (3d 9 ) charge state, becomes an important research topic in condensed matter physics [12][13][14][15].…”