Scanning gate experiments: From strongly to weakly invasive probes

Abstract

An open resonator fabricated in a two-dimensional electron gas is used to explore the transition from strongly invasive scanning gate microscopy to the perturbative regime of weak tip-induced potentials. With the help of numerical simulations that faithfully reproduce the main experimental findings, we quantify the extent of the perturbative regime in which the tip-induced conductance change is unambiguously determined by properties of the unperturbed system. The correspondence between the experimental and numerical results is established by analyzing the characteristic length scale and the amplitude modulation of the conductance change. In the perturbative regime, the former is shown to assume a disorder-dependent maximum value, while the latter linearly increases with the strength of a weak tip potential. arXiv:1709.08559v1 [cond-mat.mes-hall]

Partial local density of states from scanning gate microscopy

“…For experiments in the weakly invasive regime, the resolution of the SGM response is also limited by the width of the tip potential. 42 One way to approach the regime where the direct link is valid would be to use systems with lower Fermi energy and thus larger Fermi wavelength.…”

Signatures of folded branches in the scanning gate microscopy of ballistic electronic cavities

“…These branches have been interpreted in terms of inhomogeneous electron flow within the 2DEG, based on the analysis of quantum simulations and classical trajectory density counting performed in the presence of a weakly disordered potential [2,3]. 1 While recent works have focused on the stability of these branches when the Fermi energy is varied [6,8], and very recently branches have been observed in light propagation through soap films [9], confining gates have been found to lead to more complex SGM patterns [10][11][12][13][14][15] which are often difficult to interpret.…”

“…When a channel defined by gates beyond the QPC is progressively turned on, three experimental regimes are observed: one in which branches spread unrestrictedly, one in which branches are confined, and one where the branches have disappeared [13]. The case of a circular mirror facing a QPC has been explored experimentally and theoretically [14] as a function of the invasiveness of the tip and the degree of confinement. The length scale of the fluctuations in the SGM response attains a maximum value, which is related to the spatial extension of the tip potential, for the weakest tip strength where the tip can be treated perturbatively [16,17].…”

Energy stability of branching in the scanning gate response of two-dimensional electron gases with smooth disorder

“…In this last case, the presence of a depletion disk much larger than the Fermi wavelength results in the backscattering of the impinging electrons. Recent experiments using tunable reflectors bridged the gap between these two limits by modulating the tip strength and the electronic confinement [13].…”