Figure 1

(a) Layer structure of the $\mathrm{InAs}/\mathrm{GaAs}$ sample for magnetization, consisting of 29 layers of self-assembled InAs nanostructures. The nanostructures are located between two 24 nm GaAs layers. The repeated sequence contains a modulation doping layer, which provides electrons to the nanostructured layers. Additional doping layers (blue or dark gray) are inserted to accommodate for the depletion toward the capping layer and the undoped substrate. (b) XSTM images of different cross-sections of two stacked nanovolcanoes in the reference sample. The images reveal the presence of indium (bright spots) in the center of the nanostructures, and a clear difference in the height of the rim between the [110] and $[1\overline{1}0]$ directions. This characterization leads to a realistic description of (c) the height profile and (d) the adiabatic potential for an electron in the nanostucture.Reuse & Permissions

Figure 2

(a) Experimental curve of the magnetic moment $M$ at $T=4.2\mathrm{K}$ and 1.2 K. An Aharonov-Bohm oscillation is observed around 14 T, superimposed on a smooth background. (b) Oscillation in the magnetic moment per electron ($\mu =M/N$), obtained at 1.2 K and at 4.2 K, after subtracting the linear background from the signal, dividing by the total number of electrons $N$, and averaging over several measurements. The inset shows the first derivative of the experimental magnetic moment with respect to $B$ at $T=1.2\mathrm{K}$. (c) Calculated magnetic moment, and its derivative (inset), of a single electron in a nanostructure at different temperatures. The calculations are based on the structural parameters of the nanovolcanoes, as obtained by XSTM measurements, and accurately reproduce the Aharonov-Bohm oscillation at $B=14\mathrm{T}$.Reuse & Permissions

Figure 3

(a) The electron energy levels $E^{(e)}$ as a function of magnetic field for an ideal ring with radius 11.5 nm. The arrow indicates a changeover from a state with $\ell =0$ to a state with $\ell =-1$ as the ground state, which takes place around 5 T. (b) $E^{(e)}$ as a function of $B$ for a disc-shaped quantum dot. There are no crossings of the lower lying energy levels. (c) The realistic model of the volcanolike nanostructure reveals a changeover around 14 T.Reuse & Permissions