Magnetism and metal-insulator transition in two-dimensional electron systems formed in semiconductor interfaces

我们研究了在Si-MOSFET和Si/SiGe异质结构中形成的强关联二维电子系统的电子态和磁态。1）我们测量了自旋磁化率作为关联参数rs的函数。自旋极化率随rs单调增加; 2）平行磁场中的磁电阻主要是由自旋极化引起的; 3）对于Si/SiGe异质结构样品，即使在完全自旋极化系统中也观察到了金属相; 4）观察到了与自旋向上的电子浓度相关的对角电阻率的振荡。6）为了进行比较，我们研究了GaAs/AlGaAs场效应晶体管器件中二维电子系统的绝缘相，其中电子关联比硅系统中的弱得多。

We have studied electronic states and magnetic states in strongly correlated two-dimensional electron systems formed in Si-MOSFETs and Si/SiGe heterostructures.1) We have measured the spin susceptibility as a function of the correlation parameter rs. The spin susceptibility monotonically increases with rs.2) We found that the magnetoresistance in parallel magnetic fields is mainly caused by the spin polarization.3) We observed the metallic phase even in the completely spin polarized system for a Si/SiGe heterostructure sample.4) We have observed oscillations of the diagonal resistivity associated with the concentration of electrons having an up-spin.5) We have established the process of making field-effect-transistor samples.6) For comparison, we have investigated on the insulating phase in two-dimensional electron systems formed in GaAs/AlGaAs field-effect-transistor device, where the electron correlations are much weaker those in the silicon systems.