V g range shifted towards the more negative direction of V g . These findings indicate that this new conductance resonance is due to the state of the QD in which one extra electron is excited by the cyclotron resonance in the inner core. Figure 3 Conductance resonance and state switching. The shifted conductance resonance, recognized as the envelope of conductance spikes under the FIR illumination, shows neither width broadening nor amplitude reduction compared to the original resonance line. We have studied the influence of elevated lattice temperature up to 0.4 K in additional experiments, and confirmed that no conductance switches as observed here are induced.
Thermal activation is thus irrelevant to the phenomena.
This supports our interpretation that the new conductance resonance arises from the state containing one extra electron in the inner core. When the gate voltage is fixed at the original peak position of a given conductance resonance, the effect is of telegraph-like switches between two conductance states, as shown in Fig. As shown in Fig. The absence of background signal shows that conductance switches without illumination are negligible. The spectral line width is determined by that of the radiation from the emitters.