Abstract
The pattern of branched electron flow revealed by scanning gate microscopy shows the distribution of ballistic electron trajectories. The details of the pattern are determined by the correlated potential of remote dopants with an amplitude far below the Fermi energy. We find that the pattern persists even if the electron density is significantly reduced such that the change in Fermi energy exceeds the background potential amplitude. The branch pattern is robust against changes in charge carrier density, but not against changes in the background potential caused by additional illumination of the sample.
Highlights
Any further distribution of background potential amplitude
The pattern of branched electron flow revealed by scanning gate microscopy shows the distribution of Original content from this ballistic electron trajectories
The branch pattern is robust against changes in charge carrier this work must maintain attribution to the density, but not against changes in the background potential caused by additional illumination of the author(s) and the title of sample
Summary
As shown in figure 1(a), the 2DEG of our GaAs/AlGaAs sample is etched into a Hall bar shape that allows for measuring the longitudinal voltage VL and the source–drain current ISD in a four-terminal configuration. We illuminated the sample with red light to increase the charge carrier mobility by ionizing additional donor atoms, which changes the random background potential This so-called persistent photo conductivity in AlGaAs heterostructures is a well established effect and has been used to tune density and mobility of 2DEGs. After illumination, we can change the electron density n by applying a back-gate voltage Vbg as shown by the blue curve in figure 1(b). To remain on the second plateau for different charge carrier densities, we apply a Vbg-dependent split-gate voltage VQPC = Vb2g 24.5 V - 0.62 ́ Vbg - 1.33 V in the following measurements. The conductance variation ΔG as a function of tip position is shown in figure 2(c) with blue points marking local minima, which will be used to compare branch positions at different electron densities. A possible origin of such patterns is the presence of hard scatterers [15]
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