Thermal enhancement of interference effects in quantum point contacts.

We study an electron interferometer formed with a quantum point contact and a scanning probe tip in a two-dimensional electron gas. The images giving the conductance as a function of the tip position exhibit fringes spaced by half the Fermi wavelength. For a contact opened at the edges of a quantized conductance plateau, the fringes are enhanced as the temperature T increases and can persist beyond the thermal length l(T). This unusual effect is explained by assuming a simplified model: The fringes are mainly given by a contribution which vanishes when T→0 and has a decay characterized by a T-independent scale.

Scanning gate microscopy of a nanostructure where electrons interact.

We show that scanning gate microscopy can be used for probing electron-electron interactions inside a nanostructure. We assume a simple model made of two noninteracting strips attached to an interacting nanosystem. In one of the strips, the electrostatic potential can be locally varied by a charged tip. This change induces corrections upon the nanosystem Hartree-Fock self-energies which enhance the fringes spaced by half the Fermi wavelength in the images giving the quantum conductance as a function of the tip position.

Effect of measurement probes upon the conductance of an interacting nanosystem: detection of an attached ring by nonlocal many body effects.

We consider a nanosystem connected to measurement probes via leads. When a magnetic flux is varied through a ring attached to one lead at a distance L(c) from the nanosystem, the effective nanosystem transmission |t(s)|(2) exhibits Aharonov-Bohm oscillations if the electrons interact inside the nanosystem. These oscillations can be very large if L(c) is small and if the nanosystem has almost degenerate levels which are put near the Fermi energy by a local gate.