Spin correlations in the low-density electron system

Abstract

The authors have calculated the spin susceptibility x(q,) within a microscopic model over the full range of densities of the electron liquid in the paramagnetic state. Electron-electron interactions are described by static random-phase-approximation screening modified by a local-field correction which takes into account the exchange-correlation hole in the low-density regime. They focus attention on the dynamic properties of the system, calculating the spin-spin susceptibility x(q,). Their results can be represented in terms of a complex Stoner-like enhancement function I(q,) with an explicit dependence on the wave number q and frequency . The authors find except for very large q and that I(q,) has only a weak functional dependence on q and and is nearly real, justifying the original Stoner approximation for a wide range of q and . They find when I(q,) does develop a q dependence, that this corresponds to a buildup of short-range spin correlations in the system that goes beyond the scope of the original Stoner model. The authors results provide a first-principles determination of the density dependence of the Stoner enhancement factor. Finally, they find that paramagnons persist well away from the ferromagnetic transition