Haldane–Shastry model explained

In quantum statistical physics, the Haldane–Shastry model is a spin chain, defined on a one-dimensional, periodic lattice. Unlike the prototypical Heisenberg spin chain, which only includes interactions between neighboring sites of the lattice, the Haldane–Shastry model has long-range interactions, that is, interactions between any pair of sites, regardless of the distance between them.

The model is named after and was defined independently by Duncan Haldane and B. Sriram Shastry.^{[1] [2]} It is an exactly solvable model, and was exactly solved by Shastry.^[2]

Formulation

For a chain with

spin 1/2 sites, the quantum phase space is described by the Hilbert space . The Haldane–Shastry model is described by the Hamiltonian$$H\; =\; \backslash sum\_^L\; \backslash frac\; \backslash ,\; \backslash frac\; \backslash ,,$$where denotes the Pauli vector at the th site (acting nontrivially on the th copy of in ). Note that the pair potential suppressing the interaction strength at longer distances is an inverse square , with the chord distance between the and th sites viewed as being equispaced on the unit circle.

See also

• Inozemtsev model

Notes and References

1. Haldane . F. D. M. . Exact Jastrow-Gutzwiller resonating-valence-bond ground state of the spin-1/2 antiferromagnetic Heisenberg chain with 1/r^2 exchange . Physical Review Letters . 15 February 1988 . 60 . 7 . 635–638 . 10.1103/PhysRevLett.60.635 . 19 July 2023.
2. Shastry . B. Sriram . Exact solution of an S=1/2 Heisenberg antiferromagnetic chain with long-ranged interactions . Physical Review Letters . 15 February 1988 . 60 . 7 . 639–642 . 10.1103/PhysRevLett.60.639 . 19 July 2023.