Signatures of stripe phases in hole-dopedLa2NiO4

Abstract

We model nickelate-centered and oxygen-centered stripe phases in doped La2NiO4 materials. We use an inhomogeneous Hartree-Fock and random-phase approximation approach including both electronelectron and electron-lattice(e-l) coupling for a layer of La2NiO4. We find that whether the ground state after commensurate hole doping comprises Ni-centered or O-centered charge-localized stripes depends sensitively on the e-l interaction. With increasing e-l interaction strength, a continuous transition from an O-centered stripe phase to a Ni-centered one is found. Various low-and highenergy signatures of these two kinds of stripe phases are predicted, which can clearly distinguish them. These signatures reflect the strongly correlated spin-charge-lattice features in the vicinity of Ni-centered or O-centered stripe domains. The importance of e-l interaction for recent experiments on stripe phases is discussed.

Microscopic origin of diagonal stripe phases in doped nickelates

“…However, it numerically turns out that the energy of SC stripes is substantially larger than the one of the BC stripes, in agreement with the early study of Yi et al 62 (see Table III in Sec. V as well).…”

“…In contrast, the HF approximation used here allows one to describe charge and spin modulation with larger unit cells and hence it should provide an answer to the important question whether the description of NiO 2 planes by the simplified effective e g model described below yields results consistent with the predictions of the CT model. 60,61,62 An important aspect of these studies, qualitatively different from the pioneering work on the cuprates where the relevant models yield DWs with nonmagnetic Cu 3+ ions, 19,20,21,22,23 is that DWs in the nickelates are formed of Ni 3+ ions carrying a finite spin S = 1/2 leading to a FM polarization around them.…”

“…In fact, subsequent multiband HF calculations emphasized the relevance of the electron-lattice coupling -depending on its strength one can obtain either metal-or oxygen-centered structures. 61,62 Therefore, it appears that the semiclassical theory captures the essence of stripe physics in the nickelates.…”

“…The stripes were also obtained in the theory using either the HF approximation applied to a multiband CT model, in which both the nickel and oxygen degrees of freedom are explicitely taken into account, 60,61,62 or by the ED of finite clusters within the effective two-band model (1) extended by the coupling of e g electrons to the lattice. 63 However, due to a large number of basis states, the latter calculation has solely been done for an eight site cluster allowing only for investigating stripe phases with a small unit cell observed experimentally at high doping levels x = 1/3 and x = 1/2.…”

Phase separation models for cuprate stripe arrays

“…Such an effect arises naturally if the charged stripes have some residual magnetic interaction, and we will explore this possibility. However, in nickelates charged stripes coupled to a CDW are found to act as APBs 46 . The large Hubbard on-site repulsion U plays an important role.…”