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Schematic summary of the fabrication process (drawings not to scale). (a) A target substrate with predefined gate electrodes (10 nm Ti/30 nm Au) is covered with a 450-nm-thick LOR layer. (b) A graphene flake on a PMMA support is transferred onto LOR, aligned to the bottom electrode. ((c)-(d)) Graphene is contacted and the underlying LOR exposed with an electron beam, to achieve suspension. (e) Optical microscope image of the device (the dashed lines indicate the edges of the graphene flake); the local bottom gate is visible under the right electrode (the bar is 2 μm long). (f) Schematic top view denoting the regions 1 and 2 (coupled primarily to the two different gate electrodes).
(a) Resistance oscillation measured at T = 0.25 K as a function of V 1 and V 2. Along the dashed white line, n 1 changes while n 2 is kept fixed at . The data shown in panel (b), and in Figs. 3 and 4 are taken along this line. The inset shows the plot of R as a function of n 1 and n 2, for the V 1 and V 2 region corresponding to the parallelogram delimited by the dashed line. (b) at fixed, positive n 2 shows oscillations for negative n 1, i.e., when a pn junction is present. (c) Oscillation period , plotted as a function of . Empty squares show data taken at different values of n 1; the broken line represents the values of estimated from a simple particle-in-a-box approximation ( ).
Magnetic field dependence of measured at T = 0.25 K, at fixed n 2, along the dashed line shown in Fig. 2(a) . (a) Plot of , showing characteristic π-shift at . (b) Plot of , as a function of n 1 and B, shown for comparison with similar data reported in the literature. In (a), the broken lines indicate the values of B (B = 0, 30, 50 mT) at which the data in (c) are measured.
Energy dependence of the Fabry-Perot interference. (a) Resistance R measured at T = 0.25 K as a function of bias VDC and n 1 (at fixed n 2 along a dashed line in Fig. 2(a) ); the yellow dashed lines are guides to the eye. (b) Two representative curves of measured at and 5.2 mV, showing a π shift in the oscillation phase. (c) T-dependence of measured at . All data in this figure were taken at B = 40 mT.
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