Doped Stripes in Models for the Cuprates Emerging from the One-Hole Properties of the Insulator

Abstract

The extended and standard t-J models are computationally studied on ladders and planes, with emphasis on the small J/t region. At couplings compatible with photoemission results for undoped cuprates, half-doped stripes separating π-shifted antiferromagnetic (AF) domains are found, as in Tranquada's interpretation of neutron experiments. Our main result is that the elementary stripe "building-block" resembles the properties of one hole at small J/t, with robust AF correlations across-the-hole induced by the local tendency of the charge to separate from the spin (G. Martins et al., Phys. Rev. B60, R3716 (1999)). This suggests that the seed of half-doped stripes already exists in the unusual properties of the insulating parent compound. . Whether stripe formation is beneficial or detrimental to superconductivity is unclear, but it appears that stripes are an important ingredient of the normal state that cannot be ignored.The theoretical explanation of stripe formation is much debated. Early work reported stripes in the t-J (at large J/t with 1/r repulsions) and Hubbard (Hartree-Fock) models [3,4]. However, these stripes were insulating with hole density n h ∼1.0, different from the experimental n h ∼0.5 stripes [5]. Recently, considerable progress was made when doped stripes were reported by White and Scalapino within the standard t-J model [6] (see also Ref.[7]). In Ref.[6] the analysis was performed at couplings where two holes form d-wave pairs, and the stripes are sometimes described as a condensation of these pairs into a stripe domain-wall [8]. However, experiments are usually interpreted as holes moving freely along site-centered stripes [1]. In addition, the "extended" t-J model with hopping beyond neighboring sites, or the standard t-J model with very small J/t, are needed [9,10] to reproduce the insulator one-hole photoemission (PES) dispersion [11]. Thus, understanding metallic stripe formation requires further work and searching for stripes in the extended t-J model, particularly in regimes without hole binding and where the absence of phase separation (PS) is not controversial, is important to clarify the driving mechanism for these unusual complex structures.Building upon previous investigations [6,7], in this Letter indications of n h ∼0.5 stripes compatible with experiments [1] are reported in the extended and standard t-J models on ladders and square clusters. These stripes do not seem composed of hole pairs (although pairs forming domain-walls may be present at larger J/t than studied here [8]). They also exist in the t-J z model [12] and using classical spins [7], implying that the details of the AF spin background are unimportant for its stabilization. Moreover, our most important result is that the basic stripe "building-block" exists already in the insulator where one-hole wave functions have a complex spin structure with strong AF correlations across-the-hole, resembling the stripe spin correlations found here numerically. These results provide a rationalization for stripe formation built u...

Quasiparticles andc-axis coherent hopping in high-Tcsuperconductors

“…If these excitations actually describe a region of charge and spin separation, the dashed line branch does not correspond to the dispersion of a single quasiparticle but to the superposition of a holon and a spinon. It has been suggested that these states play a central role in the many-holes states and may be responsible for the formation of stripes [12]. As we show below, they are also relevant for the coherent hopping along the c-axis in the doped systems.…”

“…In the 18-site cluster, stripes are observed in the three holes ground state [12]. Based on the spin correlations across the hole, it has been argued that these stripes are made out of one-hole building-blocks with AFCAH [12]. In other words, the two holes wave function has a large component of the one-hole wave function of the k = (0, π) type.…”

“…These results are in agreement with previous results obtained in ladders and clusters. In the 18-site cluster, stripes are observed in the three holes ground state [12]. Based on the spin correlations across the hole, it has been argued that these stripes are made out of one-hole building-blocks with AFCAH [12].…”

“…These states have been studied recently in some detail [10,11]. The spin correlations across the hole are antiferromagnetic (AFCAH), like in 1D systems, and it has been speculated that this is an indication of charge and spin separation in the 2D t-J model [12].…”

Quantum Monte Carlo simulations of the t–Jz model with stripes on the square lattice

“…In yet another approaches, the stripes exclude hole pairing. 10 There are even more important differences regarding the origin of stripes. In Ref.…”