Jahn–Teller mechanism of stripe formation in doped layeredLa2 − xSrxNiO4 nickelates

Abstract

We introduce an effective model foreg electrons to describe quasi-two-dimensional layeredLa2 − xSrxNiO4 nickelates and study it using correlated wavefunctions on8 × 8 and6 × 6 clusters. The effective Hamiltonian includes the kinetic energy, on-site Coulomb interactions foreg electrons (intraorbitalU and Hund’sexchange JH) and thecoupling between eg electrons and Jahn–Teller distortions (static modes). The experimental groundstate phases with inhomogeneous charge, spin and orbital order at the dopingsx = 1/3 and1/2 are reproduced very well by the model. Although the Jahn–Teller distortions areweak, we show that they play a crucial role and stabilize the observed cooperativecharge, magnetic and orbital order in the form of a diagonal stripe phase atx = 1/3 doping and achequerboard phase at x = 1/2 doping.