Schwinger-Keldysh semionic approach for quantum spin systems.
We derive a path-integral Schwinger-Keldysh approach for quantum spin systems. This is achieved by means of a semionic representation of spins as fermions with imaginary chemical potential. The major simplifying feature in comparison with other representations (Holstein-Primakoff, Dyson-Maleev, slave bosons/fermions, etc.) is that the local constraint is taken into account exactly. As a result, the standard diagram technique with the usual Feynman codex is constructed. We illustrate the application of this technique for the Néel and spin-liquid states of the antiferromagnetic Heisenberg model.
Kiselev
M N
MN
Institut für Theoretische Physik, Universität Würzburg, D-97074 Würzburg, Germany.
Oppermann
R
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