Electronic Transport in Parabolic Wells

对于没有点电荷背景散射的三维电子气，预言会出现许多有趣的新现象。在量子极限的强磁场被预测为诱导集体电荷或自旋密度波态，具有类似于量子霍尔效应的新的输运性质。与他们的合作者A.C.Gossard合作，他们开发了一种方法，使用广泛的远程掺杂抛物线砷镓/铝镓1-xAs井来产生空间均匀的电子气体层，这些井的厚度可以达到三维极限。抛物线势能是通过对铝的平均浓度进行抛物线分级而产生的，在电子看来是空间均匀的正本底电荷。他们建议在稀释制冷机温度下研究强磁场中的磁输运，以研究随着电子层变厚而发生的量子霍尔效应的变化，并寻找新的集体现象。这些异质结构将通过光学和远红外测量电子的量子激发光谱，以及测量磁阻中的Shubnikov de Haas振荡来表征。

Many interesting and new phenomena are predicted to occur for a three dimensional electron gas where scattering by the background of point charges is absent. Strong magnetic fields in the quantum limit are predicted to induce collective charge- or spin- density wave states with novel transport properties analogous to the quantum Hall effect. With their collaborator, A.C. Gossard, they have developed means of producing spatially uniform layers of elctron gas using wide remotely doped parabolic gallium arsenic/aluminumxgallium1-xarsenic wells, which can be thick enough to approach the three-dimensional limit. The parabolic potential, created using parabolic grading of the average aluminum concentration, appears to the electrons as a spatially uniform positive background charge. They propose to investigate magnetotransport in strong magnetic fields at dilution refrigerator temperatures in order to study the changes which occur in the quantum Hall effect as the electron layer becomes thicker, and to search for new collective phenomena. These heterostructures will be characterized using optical and far- infrared measurements of the quantum excitation spectra of electrons, as well as measurements of Shubnikov de Haas oscillations in the magnetoresistance.