We report a conductance asymmetry of quantum point contacts (QPC) at near-zero applied current biases. The asymmetry is measured at low temperatures as a rectified dc voltage response to an applied small amplitude ac current. When measured as a function of negative gate-voltage, the rectified signal oscillates. For some of the samples this oscillatory behavior scales linearly with the applied ac current amplitude, which indicates only one step-like non-linearity in differential resistance vs. current. The value of the step is of the order of a few tens of Ohms on a background of several kOhms, and embedded in intrinsic random telegraph signal (RTS) noise. The step could be verified also by a direct measurement of differential resistance vs. dc current. We believe a two-level impurity configuration near the constriction is responsible for the step-like differential resistance.
|Journal||Physica B: Condensed Matter|
|Publication status||Published - 1994|
|Event||20th International Conference on Low Temperature Physics - Eugne, OR, United States|
Duration: 4 Aug 1993 → 11 Aug 1993
Conference number: 20
|Conference||20th International Conference on Low Temperature Physics|
|Period||04/08/1993 → 11/08/1993|