N. Schildermans

High-field magnetoexcitons in unstrained GaAs ∕ Al x Ga 1 − x As quantum dots

The magnetic field dependence of the excitonic states in unstrained GaAs/AlxGa1-xAs quantum dots is investigated theoretically and experimentally. The diamagnetic shift for the ground and the excited states are studied in magnetic fields of varying orientation. In the theoretical study, calculations are performed within the single band effective mass approximation, including band nonparabolicity, the full experimental three-dimensional dot shape and the electron-hole Coulomb interaction. These calculations are compared with the experimental results for both the ground and the excited states in fields up to 50 Tesla. Good agreement is found between theory and experiment.

Rectification effects in superconducting triangles

A superconducting microtriangle is proposed to be used as a field-dependent diode. A dc voltage generated by the triangle induced by an applied ac drive is observed close to the superconducting/normal phase boundary. This effect is due to the superposition of the asymmetric screening currents in the triangle and the ac drive. The sign of the dc voltage is an alternating function of the applied magnetic field that reflects switching of the direction of the screening currents in the structure.

Critical field enhancement in hybrid superconductor/ferromagnet mesoscopic disks

We investigated experimentally the nucleation of superconductivity in a mesoscopic hybrid structure, consisting of a thin superconducting disk covered with a ferromagnetic layer with an in-plane magnetic moment. By applying a magnetic field in the plane of the structure, the remanent magnetic state of the ferromagnet can be switched from a flux-closure state where field lines are confined inside the ferromagnet to a polarized state with nonzero stray fields at the edges. This change in the magnetic state causes a drastic modification on the superconductor/normal-state phase boundary of the hybrid sample. In the polarized state a re-entrant transition line and a strong broadening of the phase boundary are observed.

High-field magnetoexcitons in unstrainedGaAs∕AlxGa1−xAsquantum dots

The magnetic field dependence of the excitonic states in unstrained GaAs/AlxGa1-xAs quantum dots is investigated theoretically and experimentally. The diamagnetic shift for the ground and the excited states are studied in magnetic fields of varying orientation. In the theoretical study, calculations are performed within the single band effective mass approximation, including band nonparabolicity, the full experimental three-dimensional dot shape and the electron-hole Coulomb interaction. These calculations are compared with the experimental results for both the ground and the excited states in fields up to 50 Tesla. Good agreement is found between theory and experiment.

High-field magneto-excitons in unstrained GaAs/AlGaAs quantum dots

The magnetic field dependence of the excitonic states in unstrained GaAs/AlxGa1-xAs quantum dots is investigated theoretically and experimentally. The diamagnetic shift for the ground and the excited states are studied in magnetic fields of varying orientation. In the theoretical study, calculations are performed within the single band effective mass approximation, including band nonparabolicity, the full experimental three-dimensional dot shape and the electron-hole Coulomb interaction. These calculations are compared with the experimental results for both the ground and the excited states in fields up to 50 Tesla. Good agreement is found between theory and experiment.