On the origin of the temperature dependence of spin susceptibility in correlated 2D electron system

A dilute two-dimensional (2D) system of interacting electrons has tendency to spontaneous spin polarization with increase of interparticle interaction. This instability, anticipated to occur with lowering carrier density and temperature, in fact has never been observed. Here, we report temperature dependence of the spin susceptibility of a 2D electron system in Si-MOS structures measured by two different techniques: (i) χT(T) by direct thermodynamic measurements, which are sensitive to all the electrons, and (ii) χ∗(T) from quantum oscillations in vector field, sensitive to the itinerant electrons only. In the former case, the susceptibility strongly diverges as 1/T2. In the latter case we found a weak χ∗(T) dependence, only a few percent over the range T=(0.1÷1)K, which seems to agree qualitatively with the predicted interaction corrections. We provide evidences for this difference to stem from the temperature- and magnetic field-dependent exchange with carriers between the localized and itinerant electrons coexisting in the two-phase state.