If I have a 2DEG with a voltage in the $x$-direction and a $B$-Field in the $z$-direction (so I also get a hall-voltage in the $y$-direction (classicaly)). But if I do this stuff at low temperatures I can observe some quantum effects like Shubnikov-de Haas Oscillations and the Quantum Hall Effect.
I understand how the Quantum Hall Effect emerges but I can't seem to understand why the Shubnikov-de Haas Oscialltions happen.
As far as I know, if the Fermi-Energy (or chemical potential) starts to cross the density of states (as a function of energy) (which represents one Landau Level) it causes all the electrons to conduct a current. At that region the resistence rises. If the Landau Level is passed (the Fermi-Energy is between two Landau Levels) the resistence seems to drop again, but I don't know why.
What causes the Shubnikov-de Haas Oscillations? Why do Shubnikov-de Haas Oscillations occur?