The quantized Hall insulator

The quantized Hall insulator is characterized by vanishing conductivities a nd a quantized flail resistance. For low mobility samples, the quantized Ha ll insulator is obtained when the magnetic field is increased well above th e nu = 1 quantum Hall state. For higher mobility samples, a similar quantiz ation is observed when the magnetic field is increased above the nu = 1/3 f ractional quantum Hall states. This quantization, throughout the quantum Ha ll liquid-to-insulator transition, leads to a perfect semicircle relation f or the diagonal and Hall conductivities. The measurements were performed in Ge/SiGe quantum Wells and in n-type InP/InGaAs and GaAs/AlGaAs heterostruc tures.