Topological spin defects

Let us now suppose that there is a topological spin defect on site i of cell n, i.e. for any reason the site ni remains not spin-paired. Making use of the freedom of defining the cell and the numbering of the sites in the cell, without lost of generality, let us number the sites such that... 

Thus, a topological spin defect can be seen as a domain wall separating sectors with order parameters Di and Dr. 

From the very beginning of the modern era, there was strong involvement of theorists. Theoretical physicists were particularly interested in the topological defects inherent in ID systems, and the reversed spin-charge relationships of sohtons and polarons. Quantum chemists focused on the molecular-orbital theory of extended structures. Both disciplines struggled with the relative importance of electron correlations and electron—phonon interactions. 

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