Orbital control of effective dimensionality: from spin-orbital fractionalization to confinement in the anisotropic ladder system CaCu2O3

Abstract

Fractionalization of an electronic quasiparticle into spin, charge and orbital parts is a fundamental and characteristic property of interacting electrons in one dimension. However, real materials are never strictly one-dimensional and the fractionalization phenomena are hard to observe. Here we studied the spin and orbital excitations of the anisotropic ladder material CaCu2O3, whose electronic structure is not one-dimensional. Combining high-resolution resonant inelastic x-ray scattering experiments with theoretical model calculations we show that: (i) spin-orbital fractionalization occurs in CaCu2O3 along the leg direction x through the xz orbital channel as in a 1D system; and (ii) no fractionalization is observed for the xy orbital, which extends in both leg and rung direction, contrary to a 1D system. We conclude that the directional character of the orbital hopping can select different degrees of dimensionality. Using additional model calculations, we show that spin-orbital separation is generally far more robust than the spin-charge separation. This is not only due to the already mentioned selection realized by the orbital hopping, but also due to the fact that spinons are faster than the orbitons.

6 pages, 4 figure

References in corpus (5)

• Spin-Orbital Separation in the quasi 1D Mott-insulator Sr2CuO3
• Microscopic origin of spin-orbital separation in Sr2CuO3
• Spectral properties of orbital polarons in Mott insulators
• Femtosecond dynamics of magnetic excitations from resonant inelastic x-ray scattering in CaCu2O3
• Charge and Spin Fractionalization Beyond the Luttinger Liquid Paradigm

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