Pauli spin susceptibility of a strongly correlated two-dimensional   electron liquid
  Thermodynamic measurements reveal that the Pauli spin susceptibility of strongly correlated two-dimensional electrons in silicon grows critically at low electron densities - behavior that is characteristic of the existence of a phase transition. 
A. A. Shashkin, S. Anissimova, M. R. Sakr, S. V. Kravchenko, V. T.   Dolgopolov, and T. M. Klapwijk