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Thouless number and spin diffusion in quantum Heisenberg ferromagnets

Peter Kopietz
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Abstract

Using an analogy between the conductivity tensor of electronic systems and the spin stiffness tensor of spin systems, we introduce the concept of the Thouless number $g_0$ and the dimensionless frequency dependent conductance $g( ω)$ for quantum spin models. It is shown that spin diffusion implies the vanishing of the Drude peak of $g ( ω)$, and that the spin diffusion coefficient $D_s$ is proportional to $g_0$. We develop a new method based on the Thouless number to calculate $D_s$, and present results for $D_s$ in the nearest-neighbor quantum Heisenberg ferromagnet at infinite temperatures for arbitrary dimension $d$ and spin $S$.

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Peter Kopietz. 1993-07-20. Thouless number and spin diffusion in quantum Heisenberg ferromagnets. https://doi.org/10.1142/s0217984993001788

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