Comparison of 32-site exact-diagonalization results and ARPES spectral functions for the antiferromagnetic insulatorSr2CuO2

Abstract

We explore the success of various versions of the one-band t-J model in explaining the full spectral functions found in angle-resolved photoemission spectra for the prototypical, quasi-two-dimensional, tetragonal, antiferromagnetic insulator Sr 2 CuO 2 Cl 2 . After presenting arguments justifying our extraction of A(k, ) from the experimental data, we rely on exact-diagonalization results from studies of a square 32-site lattice, the largest cluster for which such information is presently available, to perform this comparison. Our work leads us to believe that ͑i͒ a one-band model that includes hopping out to third-nearest neighbors, as well three-site, spin-dependent hopping, can indeed explain not only the dispersion relation, but also the quasiparticle lifetimes-only in the neighborhood of kϭ( /2,0) do we find disagreement; ͑ii͒ an energy-dependent broadening function, ⌫(E)ϭ⌫ 0 ϩAE, is important in accounting for the incoherent contributions to the spectral functions. ͓S0163-1829͑97͒07034-3͔

Theory for Slightly Doped Antiferromagnetic Mott Insulators

“…for one or two holes or electrons, there exists, however, some inconsistancy in the detail of the comparison. Namely, at some momenta k's the spectral weights Z k = | Ψ k |c kσ |Ψ 0 | 2 / Ψ 0 |c † kσ c kσ |Ψ 0 computed for the one doped hole case using |Ψ k = |Ψ 1 are much larger than the exact results [8]. This may indicate that the quasi-particle states do not exist everywhere in the Brillouin zone.…”

“…Substituting WF |Ψ ′ 1 and the quasi-particle |Ψ 1 into |Ψ k and computing Z k suffices to reproduce the variation of the spectral weights obtained in the exact results [8]. States described by |Ψ ′ 1 have smaller Z k 's and are thus with a strong incoherent character.…”

“…But so far most experiments do not support the coexistence. In addition, there has been not enough understanding on various properties found in the exact results of the t-J type models on finite clusters [5,6,8,9,10,11,12] in terms of the many-particle wave functions (WF's).…”

“…The single hole/electron behavior and its dispersion have been studied using various approaches on the t-t ′ -t ′′ -J model [5,6,7,8,9,10]. However, these studies on doping holes and electrons into the system only emphasize the asymmetry resulting from the different signs of t ′ and t ′′ for the corresponding Hamiltonians.…”

Charge carrier correlation in the electron-dopedt−Jmodel

“…The best fitting to ARPES results on Sr 2 CuO 2 Cl 2 yields t =1, tЈ = −0.3, and tЉ = 0.2. 17 In the case of hole doping, c i † is a spin ͑or electron͒ creation operator. To describe electron-doped materials it is usual to apply the electron-hole transformation, 3 c i → ã i † , where ã i † is a hole creation operator.…”