Search for Multiple Step Integer Quantum Hall Transitions

Abstract

Recent experiments in the integer quantum Hall regime seem to find direct transitions from a quantum Hall state with Hall conductance $\sigma_{xy} = n e^2/h $ with integer $n > 1$, to an insulating state in weak magnetic fields. We study this issue using a variation of the tight-binding lattice model for non-interacting electrons. Although quantum Hall transitions with change in Hall conductance $n e^2/ h$ with $n > 1$ do exist in our model for special tuning of parameters, they generically split into quantum Hall transitions with the Hall conductance changing by $e^2 / h$ at each transition. This suggests that a generic multiple step quantum Hall transition is incompatible with a non-interacting electron picture.