Determine the origin of the intermediate QPC-voltage discontinuity

Determine the physical origin of the discontinuity observed near the quantum point contact voltage V_QPC ≃ −0.2 V in the edge-magnetoplasmon resonator, including whether it results from localized states and charging effects induced by the higher electron density beneath the quantum point contact.

Background

During measurements of the resonance as a function of magnetic field and QPC voltage, the authors observe a discontinuity near V_QPC ≃ −0.2 V in addition to the main pinch-off feature near −0.6 V. They suggest that the discontinuity may be caused by the voltage applied to the top gates, which could produce a higher electron density below the QPC than elsewhere in the resonator and thereby generate localized states and charging effects.

The proposed mechanism is explicitly presented as only a hypothesis, leaving the physical origin of this discontinuity unresolved.

References

Another discontinuity is observed around $V_\mathrm{QPC} \simeq -0.2$~\SI{}\volt whose origin is not fully understood. Our current hypothesis is that this is linked to the voltage applied on top gates $V_G = -75$~\SI{}\milli\volt.

— Electrostatic splitting of an Edge Magnetoplasmon Resonator  (2609.05188 - Kouamé et al., 4 Sep 2026) in Section 3.2, “Splitting of the cavity by a QPC”