Parallel magnetic field induced magnetoresistance peculiarities of the double quantum well filled with electrons or holes

In In x Ga 1 - x As/n-GaAs double quantum wells (DQWs) containing an electron gas, the magnetoresistance (MR) peculiarities under parallel magnetic fields caused by the passing of the tunnel gap edges through the Fermi levelare revealed. Peculiarities positioned in high fields (∼ 30 T) can only be explained if the spin-splitting of the In x Ga 1 - x As conduction band is considered, that was neglected in the GaAs/AlGaAs heterostructures, for which solely the effects of this nature have been observed so far. In the Ge/p-Ge 1 - x Si x DQWs containing a hole gas, local MR peculiarities under parallel fields are discovered as well. But the tunnel gap in these DQWs is too narrow to be responsible for these observations. We suppose, they are due to a complicated shape of the hole confinement subbands.