Emerging phenomena in two-dimensional electron system in intermediate magnetic fields

The interlayer electron-electron interaction in bilayer two-dimensional electron system has been studied in tilted magnetic fields through electron drag measurements. In intermediate magnetic fields, where the temperature of electrons is comparable or larger than Landau level spacing, electrons near Fermi level can access more than one Landau level and inter-Landau level scatterings play an important role in transport properties of the system. In such a regime, we observed that the resonant 2kF interlayer phonon exchange present in perpendicular magnetic fields is suppressed by moderate in-plane magnetic fields. Furthermore, in the absence of such resonant phonon exchange, the magneto-enhancement of drag is nearly temperature-independent and has a highly unusual B3⊥ field dependence. We argue that the drastic suppression of 2 kF phonon exchange in tilted magnetic fields might be related to the substantial change in out-of-plane Lorentz force on electrons by in-plane component of fields during the 2kF scattering process. We also argue that highly unusual temperature and field dependences of drag in tilted magnetic fields might be a consequence of fully-activated inter-Landau level scatterings, which are often neglected.