Novel energy scale in the interacting two-dimensional electron system evidenced from transport and thermodynamic measurements

We study how the non-Fermi-liquid two-phase state reveals itself in transport properties of high-mobility Si-MOSFETs. We have found features in zero-field transport, magnetotransport, and thermodynamic spin magnetization in a 2D correlated electron system that may be directly related with the two-phase state. The features manifest above a density-dependent temperature T* that represents a high-energy scale, apart from the Fermi energy. More specifically, in magnetoconductivity, we found a sharp onset of the regime δσ(B,T)∝(B/T)² above a density-dependent temperature Tₖᵢₙₖ(n), a high-energy behavior that ``mimics'' the low-temperature diffusive interaction regime. The zero-field resistivity temperature dependence exhibits an inflection point Tinfl(n). In thermodynamic magnetization, the weak-field spin susceptibility per electron ∂χ/∂n changes sign at TdM/dn(n). All three notable temperatures, Tₖᵢₙₖ,0.16em0exTinfl, and TdM/dn behave critically ∝(n-nc), are close to each other, and are intrinsic to high-mobility samples solely; we therefore associate them with an energy scale T* caused by interactions in the 2DE system.