Zeros in single-channel transmission through double quantum dots.

Area of Science:

• Quantum physics
• Condensed matter physics
• Mesoscopic systems

Background:

• Quantum dots are semiconductor nanostructures with tunable electronic properties.
• Understanding electron transport in coupled quantum dot systems is crucial for quantum technologies.
• Transmission zeros in quantum systems are points of zero probability for particle passage.

Purpose of the Study:

• To investigate single-channel transmission through a double quantum dot system.
• To explain the origin and nature of transmission zeros in this system.
• To analyze the role of inter-level interference and dot symmetry on transmission characteristics.

Main Methods:

• Development of a simple theoretical model for a double quantum dot system.
• Utilizing S-matrix theory to describe electron transmission.
• Employing an effective non-Hermitian Hamilton operator (H(eff)) to analyze system dynamics.
• Investigating the energy dependence of decay widths for system eigenstates.

Main Results:

• Transmission zeros in the double quantum dot primarily originate from destructive interference between adjacent energy levels.
• First-order transmission zeros cause a phase jump of pi in the transmission amplitude.
• Second-order transmission zeros, observed in identical dots, do not cause phase jumps due to vanishing state width at the zero energy.
• The decay widths of resonance states are strongly energy-dependent and influenced by the spectral properties of individual dots.

Conclusions:

• The model successfully explains the origin of transmission zeros in double quantum dots.
• Interference effects and dot symmetry are key factors determining the order and behavior of transmission zeros.
• The findings provide insights into controlling electron transport and phase coherence in quantum dot systems.