Novel Energy Scale in the Interacting 2D 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 novel high-energy scale, apart from the Fermi energy. More specifically, in magnetoconductivity, we found a sharp onset of the novel regime $\delta \sigma(B,T) \propto (B/T)^2$ above a density-dependent temperature $T_{\rm kink}(n)$, a high-energy behavior that "mimics" the low-temperature diffusive interaction regime. The zero-field resistivity temperature dependence exhibits an inflection point $T_{\rm infl}(n)$. In thermodynamic magnetization, the weak-field spin susceptibility per electron, $\partial \chi /\partial n$ changes sign at $T_{dM/dn}(n)$. All three notable temperatures, $T_{\rm kink}$, $T_{\rm infl}$, and $T_{d M/ d n}$, behave critically $\propto (n-n_c)$, 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.