Spin-charge decoupling and the photoemission line-shape in one dimensional insulators

The recent advances in angle resolved photoemission techniques allowed the unambiguous experimental confirmation of spin charge decoupling in quasi one dimensional (1D) Mott insulators. This opportunity stimulates a quantitative analysis of the spectral function $A(k,ω)$ of prototypical one dimensional correlated models. Here we combine Bethe Ansatz results, Lanczos diagonalizations and field theoretical approaches to obtain $A(k,ω)$ for the 1D Hubbard model as a function of the interaction strength. By introducing a {\it single spinon approximation}, an analytic expression is obtained, which shows the location of the singularities and allows, when supplemented by numerical calculations, to obtain an accurate estimate of the spectral weight distribution in the $(k,ω)$ plane. Several experimental puzzles on the observed intensities and line-shapes in quasi 1D compounds, like ${\rm SrCuO_2}$, find a natural explanation in this theoretical framework.

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