Nickelates: A Tale of Two Stories

This talk will involve two stories; a) metal-insulator transition in BiNiO3, and b) superconductivity in infinite-layer nickelates (RENiO2, RE=Nd/La).

In the first story, using ab initio electronic structure and slave rotor theory calculations, we demonstrate [1,2] that hybridization-switching induced Mott transition happens in BiNiO3. We show that these systems exhibit a breathing phonon driven Bi to oxygen hybridization-wave instability which conspires with strong correlations on Ni site to induce a Mott insulator. In contrast to ABO3 perovskites with passive A-site cations, these Mott insulators with active A-site orbitals like Bi are shown to undergo a pressure induced insulator to metal transition accompanied by a colossal volume collapse due to ligand hybridization switching.

In the second story, we explore superconductivity in NdNiO2 and LaNiO2 employing a first-principles derived low-energy model Hamiltonian, consisting of two orbitals: Ni x2 -y2 , and an axial orbital. The axial orbital is constructed out of Nd/La d, Ni 3z2 -r2 and Ni s characters. Calculation of the superconducting pairing symmetry and pairing eigenvalue of the spin-fluctuation mediated pairing interaction underlines the crucial role of inter-orbital Hubbard interaction in superconductivity, which turns out to be orbital-selective. The axial orbital brings in materials dependence in the problem, making NdNiO2 different from LaNiO2 , thereby controlling the inter-orbital Hubbard interaction assisted superconductivity.[3,4]

[1] Atanu Paul, Anamitra Mukherjee, Indra Dasgupta, Arun Paramekanti, and Tanusri Saha-Dasgupta, Phys. Rev. Lett. 122, 016404 (2019).

[2] Atanu Paul, Anamitra Mukherjee, Indra Dasgupta, and Tanusri Saha-Dasgupta, Phys. Rev. Res,  2, 013333 (2020).

[3] Priyo Adhikary, Subhadeep Bandyopadhyay, Tanmoy Das, Indra Dasgupta, and Tanusri Saha-Dasgupta, Phys. Rev. B 102, 100501(R) (2020).

[4] Priyo Adhikary, Subhadeep Bandyopadhyay, Tanmoy Das, Indra Dasgupta, and Tanusri Saha-Dasgupta,  Phys. Rev. B 102, 220502(R) (2020).