Schematic sample layout (top part) and zoom-in micrographs of the IDT and the split-gate regions. The dimensions of the IDT and the split gate as well as the coordinate system are indicated in the figure.
Transconductance dependent on the gate and bias voltage, obtained by numerical differentiation from dc measurements of . Dark shade indicates high transconductance. indicates the depletion threshold.
(a) Current as a function of gate voltage at bias for SAW powers from . (b) Differential change of current as a function of SAW amplitude and gate voltage. Tag symbols refer to the four frames in panel (c). marks the depletion threshold. (c) Barrier potential along for four different pairs of values at the instant when the SAW minimum is at . Harmonic confinement in the direction, only shown in the rightmostframe, causes 1D quantization. 1D subband minima and their modulation are indicated; is the chemical potential.
(a) Change of current dependent on the gate voltage and SAW amplitude. Dark shades indicate an increase of current with SAW amplitude. (b) Current traces along the vertical lines indicated in (a); labels indicate in volts. The marker point A indicates the region of close-to-equilibrium transport, while B marks the region of nonequilibrium transport.
Black curves: Dot depth for the close-to-equilibrium case corresponding to point A in Fig. 4 (lower curve: barrier height of is measured from the chemical potential and SAW amplitude of ) and the nonequilibrium regime corresponding to point B in Fig. 4 (upper curve: barrier height of and SAW amplitude of ) vs coordinate along the channel. The channel center is at . Gray curves: and for and . Numbers at the right indicate the number of electron states in a dot of depth at position . Arrows indicate where the moving dot gets isolated from the source reservoir in the two cases.
Calculated potential along the channel at different times. Gray areas indicate the source and drain Fermi reservoirs. (a) Close-to-equilibrium case, same parameters as in Fig. 5. A single electron is captured from the source reservoir by a shallow dot and transferred through the channel. (b) Nonequilibrium regime, same parameters as in Fig. 5 [Note the different scales in (a) and (b).] The potential is shown at time when a deep dot separates from the source reservoir at the position , and at later when the dot is shallowest and all electrons except one have been ejected.
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