Counterflow of electrons in two isolated quantum point contacts

Area of Science:

• Condensed Matter Physics
• Quantum Transport Phenomena
• Mesoscopic Physics

Background:

• Quantum point contacts (QPCs) are fundamental building blocks in quantum electronics.
• Understanding interactions between adjacent, isolated electronic components is crucial for device development.
• Previous studies have explored QPC behavior, but inter-device interactions under specific bias conditions remain an active research area.

Purpose of the Study:

• To investigate the interaction between two electrically isolated quantum point contacts (QPCs).
• To characterize the generation of electric current in an unbiased QPC due to a biased adjacent QPC.
• To elucidate the underlying mechanism responsible for the observed counterflow current.

Main Methods:

• Experimental setup involving two adjacent, electrically isolated QPCs.
• Application of a source-drain bias to one QPC (the drive QPC).
• Measurement of electric current in the second, unbiased QPC (the detector QPC).
• Systematic variation of QPC tuning and bias conditions to optimize current generation.

Main Results:

• A finite electric current was detected in the unbiased detector QPC when the drive QPC was subjected to a high source-drain bias.
• The generated current in the detector QPC consistently flowed in the opposite direction to the drive QPC's current (counterflow phenomenon).
• Maximum generated current was observed when the detector QPC was near a conductance plateau transition and the drive QPC was nearly pinched-off.

Conclusions:

• The observed counterflow current is attributed to an asymmetric phonon-induced excitation of electrons in the detector QPC's leads.
• This interaction demonstrates a novel mechanism for generating current in unbiased quantum devices.
• The findings provide valuable insights into electron-phonon interactions and non-local transport effects in mesoscopic systems.