J. Klijn

Direct comparison between potential landscape and local density of states in a disordered two-dimensional electron system.

The local density of states (LDOS) of the adsorbate-induced two-dimensional electron system (2DES) on n-InAs(110) is studied by scanning tunneling spectroscopy. In contrast to a similar 3DES, the 2DES LDOS exhibits 20 times stronger corrugations and rather irregular structures. Both results are interpreted as consequences of weak localization. Fourier transforms of the LDOS reveal that the k values of the unperturbed 2DES still dominate the 2DES, but additional lower k values contribute. To clarify the origin of the LDOS patterns, we measure the potential landscape of the 2DES area. We use it to calculate the expected LDOS and find reasonable agreement between calculation and experiment.

Comparing measured and calculated local density of states in a disordered two-dimensional electron system

Abstract The local density of states (LDOS) of the adsorbate induced two-dimensional electron system (2DES) on n-InAs(110) is studied by low-temperature scanning tunneling spectroscopy. In contrast to a similar 3DES, the 2DES LDOS exhibits 20 times stronger corrugations and rather irregular structures. Both results are interpreted as a consequence of weak localization. Fourier transforms of the LDOS reveal that the k-values of the unperturbed 2DES still dominate the 2DES, but additional lower k-values contribute significantly. To clarify the origin of the LDOS patterns, we measure the potential landscape of the same 2DES area allowing to calculate the expected LDOS from the single particle Schrodinger equation and to directly compare it with the measured one.

Visualizing the Influence of Interactions on the Nanoscale: Simple Electron Systems

Scanning tunneling spectroscopy (STS) is used to investigate the local density of states of the paradigmatic electron system located in the quasi‐parabolic conduction band of InAs. The n‐InAs(110) surface is used to investigate the system in all dimensionalities (0D‐3D) at low temperature T = 6 K and in magnetic fields up to B = 6 T. Depending on the dimensionality and the B‐field, we identify different types of electron phases. In particular, we find Bloch‐like wave functions scattered at dopants in 3D at B = 0 T, more complex wave functions reminiscent of weak localization in 2D at B = 0 T and drift states in 2D and 3D at B = 6 T. In 1D, we find surprisingly that the results are explained by a single‐particle calculation, although the energy scales are dominated by electron‐electron interaction.

Comparing the local density of states of three- and two-dimensional electron systems by low-temperature scanning tunneling spectroscopy

Abstract Scanning tunneling spectroscopy performed at T=6 K is used to investigate the local density of states (LDOS) of electron systems in the bulk conduction band of InAs. In particular, the 3DES of the n-doped material and an adsorbate-induced 2DES located at the surface are investigated at B =0 and 6 T . It is found that the 3DES at B=0 T can be described by Bloch states weakly interacting with the potential disorder. The 2DES at B=0 T exhibits much stronger LDOS corrugations revealing the tendency of weak localization. In a magnetic field both systems show drift states, which are expected in 2D, but are surprising in 3D, where they point to a new electron phase consisting of droplets of quasi 2D-systems.

Low Density Two-Dimensional Electron Systems Studied by Scanning Tunneling Spectroscopy

A two-dimensional electron system (2DES) belonging to the InAs conduction band has been prepared by depositing tiny amounts of adsorbates on the InAs(110) surface. Photoemission has been used to determine the resulting 2DES subband energies. Since the 2DES is close to the surface, it could be probed by low-temperature scanning tunneling spectroscopy. In zero magnetic field we find strong and rather irregular corrugations of the local density of states (LDOS), which are interpreted as due to the tendency of a 2DES to weakly localize. Applying a magnetic field leads to Landau quantization and to a dramatic change of the LDOS, which is now composed of drift states running along equipotential lines.