Vertical tunneling between two quantum dots in a transverse magnetic field

Tunneling between two quantum dots is studied at low temperatures. The quantum dots are formed by the combined sidewall confinement and vertical confinement in an ${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As-GaAs triple-barrier diode with a conducting diameter of 180 nm. The fine structure that is observed in the main resonance peaks of the current-voltage characteristics is related to lateral quantization effects. Electrons tunnel between zero-dimensional (0D) states in the two coupled quantum dots. A magnetic field applied perpendicular (transverse) to the tunneling direction shifts the main (2D) resonance peaks to higher bias and causes a substantial broadening. Within the fine structure we find that the resonance positions are virtually magnetic-field independent, whereas the resonance amplitudes show significant variations with increasing magnetic field; a simple model is developed to describe this behavior in terms of the magnetic-field dependence of the interdot transition probabilities.