Figure 2
(a) Charge stability diagram measured for the device at B = 1.2 T, i.e., along the dashed line A in figure 1g. It is seen that a stripe of the ZBCP structure appears in every Coulomb blockade diamond found in the figure, irrespective of the quasi-particle occupation number parity in the QD. (b) and (c) Corresponding differential conductance line-cut plots of the measurements at a series of values of Vbg. The plots shown in panel (b) are the differential conductance measurements at Vbg ranging from 5.15 V to 5.4 V, while the plots shown in panel (c) are that at Vbg ranging from 5.4 V to 5.835 V. For clarity, these line-cut plots are shifted in such a way that values of the differential conductance at Vsd = 0 μV in these line cuts are successively placed 0.005 e2/h higher than the values of their adjacent, lower gate-voltage line cuts, while their actual zero-bias conductance values are represented by their gray-scale colors. Here, in (b) and (c), the existence of a ZBCP structure in every Coulomb blockade diamond is more clearly displayed. An overall low differential conductance gap (with its two edges indicated by two arrows on top of each panel) in the low bias voltage region due to the presence of the proximity effect induced InSb superconducting energy gap and its weak dependence on Vbg can also be identified in (b) and (c). In addition, a few line cuts are highlighted by thicker lines in (b) and (c) in order to help the reader to see the characteristic features in the plots.
