Hole superconductivity in infinite-layer nickelates

After the significant discovery of the hole-doped nickelate compound Nd0.8Sr0.2NiO2, an analysis of the electronic structure, orbital components, Fermi surfaces and band topology could be helpful to understand the mechanism of its superconductivity. Based on the first-principles calculations, we find that Ni $3d_{x^2-y^2}$ states contribute the largest Fermi surface. $Ln~5d_{3z^2-r^2}$ states form an electron pocket at Γ, while 5dxy states form a relatively bigger electron pocket at A. These Fermi surfaces and symmetry characteristics can be reproduced by our two-band model, which consists of two elementary band representations: B1g@1a ⊕ A1g@1b. We find that there is a band inversion near A, giving rise to a pair of Dirac points along M–A below the Fermi level upon including spin-orbit coupling. Furthermore, we have performed the DFT+Gutzwiller calculations to treat the strong correlation effect of Ni 3d orbitals. In particular, the bandwidth of $3d_{x^2-y^2}$ has been renormalized largely. After the renormalization of the correlated bands, the Ni 3dxy states and the Dirac points become very close to the Fermi level. Thus, a hole pocket at A could be introduced by hole doping, which may be related to the observed sign change of Hall coefficient. By introducing an additional Ni 3dxy orbital, the hole-pocket band and the band inversion can be captured in our modified model. Besides, the nontrivial band topology in the ferromagnetic two-layer compound La3Ni2O6 is discussed and the band inversion is associated with Ni $3d_{x^2-y^2}$ and La 5dxy orbitals.

show abstract

“…Note added . While finalizing the present paper, similar works on nickelates were published [ 36–40 ].…”

Section: Discussionmentioning

confidence: 93%

Electronic structures and topological properties in nickelatesLnn+1NinO2n+2

Gao

Peng

Wang

et al. 2020

National Science Review

View full text Add to dashboard Cite

show abstract

“…Note added -At the stage of finishing the manuscript, we noticed related theoretical works for nickelates [43][44][45][46][47][48][49][50] . The paring of hole carriers in the oxygen pπ orbitals is discussed in Ref.…”

Section: Discussionmentioning

confidence: 99%

“…The paring of hole carriers in the oxygen pπ orbitals is discussed in Ref. 45 . First-principles simulations within GGA have been worked out in Refs.…”

Section: Discussionmentioning

confidence: 99%

Effective Hamiltonian for nickelate oxides Nd1−xSrxNiO2

Jin

Wang

et al. 2020

Phys. Rev. Research

110

View full text Add to dashboard Cite

We derive the effective single-band Hamiltonian in the flat NiO2 planes for nickelate compounds Nd1−xSrxNiO2. We first implement the first-principles calculation to study electronic structures of nickelates using the Heyd-Scuseria-Ernzerhof hybrid density functional and derive a three-band Hubbard model for Ni-O pdσ bands of Ni + 3d x 2 −y 2 and O 2− 2p x/y orbitals in the NiO2 planes. To obtain the effective one-band t-t -J model Hamiltonian, we perform the exact diagonalization of the three-band Hubbard model for the Ni5O16 cluster and map the low-energy spectra onto the effective one-band models. We find that the undoped NiO2 plane is a Hubbard Mott insulator, and the doped holes primarily locate on Ni sites. The physics of the NiO2 plane is a doped Mott insulator, described by the one-band t-t -J model with t = 265 meV, t = −21 meV and J = 28.6 meV. We also discuss the electronic structure for the "self-doping" effect and heavy fermion behavior of electron pockets of Nd 3+ 5d character in Nd1−xSrxNiO2. arXiv:1909.07427v2 [cond-mat.supr-con]

show abstract

“…On the other hand, the nickelates have larger d p and are classified as Mott-Hubbard type [3,6,10,17,20,22]. Because there is nonzero hybridization between Ni 3d x 2 −y 2 and O 2p orbitals, some of the holes should be doped into oxygen 2p orbitals [16,27,36]. However, the amount should be smaller than that of the cuprates.…”

Section: Materials: D 9 Nickelatesmentioning

confidence: 99%

Magnetic exchange coupling in cuprate-analog d9 nickelates

Nomura

Nomoto

Hirayama

et al. 2020

Phys. Rev. Research

View full text Add to dashboard Cite

Motivated by the recent discovery of superconductivity in doped NdNiO 2 , we study the magnetic exchange interaction J in layered d 9 nickelates from first principles. The mother compounds of the high-T c cuprates belong to the charge-transfer regime in the Zaanen-Sawatzky-Allen diagram and have J larger than 100 meV. While this feature makes the cuprates very different from other transition metal oxides, it is of great interest whether layered d 9 nickelates can also have such a large J. However, one complexity is that NdNiO 2 is not a Mott insulator due to carrier doping from the block layer. To compare the cuprates and d 9 nickelates on an equal basis, we study RbCa 2 NiO 3 and A 2 NiO 2 Br 2 (A denotes a cation with a valence of 2.5+), which were recently designed theoretically by block-layer engineering. These nickelates are free from the self-doping effect and belong to the Mott-Hubbard regime. We show that these nickelates share a common thread with the high-T c cuprates in that they also have a significant exchange interaction J as large as about 100 meV.

show abstract

Hole superconductivity in infinite-layer nickelates

Cited by 43 publications

References 32 publications

Electronic structures and topological properties in nickelatesLnn+1NinO2n+2

Electronic structures and topological properties in nickelatesLnn+1NinO2n+2

Effective Hamiltonian for nickelate oxides Nd1−xSrxNiO2

Magnetic exchange coupling in cuprate-analog d9 nickelates

Contact Info

Product

Resources

About