Orbital Ordering, New Phases, and Stripe Formation in Doped Layered Nickelates

TL;DR

This study explores the complex ground-state properties of doped layered nickelates using numerical methods on an orbital-degenerate Hubbard model, revealing new magnetic phases, orbital orderings, and the roles of Coulombic and phononic interactions.

Contribution

It introduces novel antiferromagnetic phases and orbital orderings in doped nickelates, highlighting the interplay of Coulombic and phononic effects in stripe formation.

Findings

Confirmation of Néel state in undoped nickelates

Discovery of CE- and E-type antiferromagnetic phases at x=1/2

Orbital ordering in checkerboard charge-ordered states

Abstract

Ground-state properties of layered nickelates are investigated based on the orbital-degenerate Hubbard model coupled with lattice distortions, by using umerical techniques. The N\'eel state composed of spin S=1 ions is confirmed in the undoped limit x=0. At x=1/2, novel antiferromagnetic states, called CE- and E-type phases, are found by increasing the Hund's coupling. (3 x^2 - r^2 / 3 y^2 - r^2)-type orbital ordering is predicted to occur in a checkerboard-type charge-ordered state. At x=1/3, both Coulombic and phononic interactions are found to be important, since the former stabilizes the spin stripe, while the latter leads to the striped charge-order.