Heisenberg spin chain

Figure 5 Diamagnetic rings currents, Nx z), of half-filled Pariser-Parr-Pople models for regular polygons with D h symmetry. The dashed line at 2 = U/4 t0 = 1.17 corresponds to standard parameters z = 0 is the Hiickel limit of free electrons, while z 1 is the strong-correlation limit of antiferromagnetic Heisenberg spin chain with vanishing ring currents [50].

For negative values of t, we obtain the uniform Heisenberg spin chain with antiferromagnetic coupling which has a nondegenerate singlet ground state. 

X. Peng, J. Du, D. Suter, Quantum phase transition of ground-state entanglement in a Heisenberg spin chain simulated in an NMR quantum computer, Phys. Rev. A 71 (2005) 012307. 

Figure 12.15 Schematic representation of the resonating vaience bonds (RVB) in the reguiar Heisenberg AFM chain. The arrows indicate the unpaired eiectron spins and the dotted iines denote the bonds.

Figure 12.19 The plot of CI(%J) vs. zJliksT) for p-CNPNN with C= 4jt x 0.375 cm K moh and zJIkg = +3.0 K. The full and dashed curves show the theoretical results of a square lattice and linear chain of Heisenberg spin with S =, respectively. The dotted line is the Curle-Welss law, CI XpT) = 1 - 0T...

An interesting feature of the spin system of this LB film was revealed by temperature dependent ESR measurements [76-78]. The temperature dependence of spin susceptibility of the LB film together with that of powder sample is shown in Figure 14.10. The magnetic properties in both LB and powder state were adequately explained by the random-exchange Heisenberg antiferromagnetic chain (REHAC) model. 

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