Lai K, Pan W, Tsui D C, Lyon S, Mühlberger M, Schäffler F
Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA.
Phys Rev Lett. 2004 Oct 8;93(15):156805. doi: 10.1103/PhysRevLett.93.156805.
Magnetotransport properties are investigated in a high-mobility two-dimensional electron system in the strained Si quantum well of a (100) Si(0.75)Ge(0.25)/Si/Si(0.75)Ge0.25 heterostructure, at temperatures down to 30 mK and in magnetic fields up to 45 T. We observe around nu=1/2 the two-flux composite fermion (CF) series of the fractional quantum Hall effect (FQHE) at nu=2/3, 3/5, 4/7, and at nu=4/9, 2/5, 1/3. Among these FQHE states, the nu=1/3, 4/7, and 4/9 states are seen for the first time in the Si/SiGe system. Interestingly, of the CF series, the 3/5 state is weaker than the nearby 4/7 state and the 3/7 state is conspicuously missing, resembling the observation in the IQHE regime that the nu=3 is weaker than the nearby nu=4 state. Our results can be quantitatively understood in the picture of CF's with the valley degree of freedom.
在温度低至30 mK、磁场高达45 T的条件下，研究了（100）Si(0.75)Ge(0.25)/Si/Si(0.75)Ge0.25异质结构的应变硅量子阱中高迁移率二维电子系统的磁输运特性。我们在ν = 1/2附近观察到分数量子霍尔效应（FQHE）的双通量复合费米子（CF）系列，分别对应于ν = 2/3、3/5、4/7以及ν = 4/9、2/5、1/3。在这些FQHE态中，ν = 1/3、4/7和4/9态是首次在Si/SiGe系统中被观测到。有趣的是，在CF系列中，3/5态比附近的4/7态弱，且明显没有3/7态，这类似于在整数量子霍尔效应（IQHE）区域中ν = 3比附近的ν = 4态弱的观测结果。我们的结果可以在考虑谷自由度的CF图像中得到定量理解。
