Figure 2
From: Enhanced electron-phonon coupling for a semiconductor charge qubit in a surface phonon cavity
Phonon bandgap in a BR.
(a) A schematic diagram for Device A used for the study of Bragg reflection. A SAW packet is launched by applying Vex to the left IDT. PCs placed in a gap of D = 160 μm are used to detect SAWs reflected between the two BRs. (b) The pulse pattern used for the Bragg-reflection measurements. When the SAW wave packet generated by Vex arrives at the PC, it oscillates the PC’s electric potential as ϕPC. This oscillation can be demodulated by applying Vdet and the measured current Idet across the PC constitutes the convoluted signal of Vdet and ϕPC, allowing us to extract the SAW signal. (c) PC current differentiated with respect to td plotted as a function of delay time at 4 K. EM crosstalk, direct wave packet (d-SAW), 1st and 2nd reflected wave packets (r1- and r2-SAW) can be observed. Inset: Comparisons of the signals measured at i-th PC defined by gates Gi and G0. Vertical offsets and black lines are applied to highlight the phase evolution. (d) Theoretical calculations of the expected wave packets at PC2 by the 1D COM theory. (e,f) Frequency dependence of the oscillation amplitudes Adet in 
at some delay times (e) measured with PC2 at 0.3 K and (f) simulated by the 1D COM theory. While the spectrum of the d-SAW packet reflects the Fourier spectrum of the incident wavepacket, that of r-SAW measures the phonon bandgap of the BRs.
