Edge channels in integer and fractional quantum-Hall regime investigated by magnetocapacitance

We have evaluated the width of edge channels in the fractional and integer quantum-Hall (QH) regime by the magnetocapacitance measurement between a gate and two-dimensional electron system in GaAs/AlGaAs heterostructures. The frequency dependence of the magnetocapacitance between 100 Hz and 1 MHz has been measured at temperatures between 35 mK and 0.4 K. At the fractional QH regime, the total width of the edge channels is found to be 2.5 and 9 μm at 35 mK at the QH plateaux of filling factor ν= 1 3 and 2 3 , respectively. In the integer QH regime, the temperature dependence of the edge channel width is almost flat in the range of 35 mK–0.4 K. At the QH plateau of ν=1 due to spin-splitting Landau level, the width of total edge channel is almost the same value with that at ν=2. The width at ν=3 is also comparable to that at ν=4, although the residual bulk conductivity of ν=3 is an order of magnitude larger than that of ν=4.