Andreev-Coulomb Drag in Coupled Quantum Dots

Area of Science:

• Condensed matter physics
• Quantum electronics
• Mesoscopic physics

Background:

• Coulomb drag is a phenomenon where charge carriers in one conductor induce a current in a nearby conductor due to electrostatic interactions.
• Previous studies observed Coulomb drag in normal coupled quantum dot devices, attributing it to electron-hole asymmetry and interactions.

Purpose of the Study:

• To investigate methods for enhancing the Coulomb drag effect in quantum dot systems.
• To explore the role of superconducting electrodes in modulating Coulomb drag.
• To identify control mechanisms and distinguishing features of the enhanced drag.

Main Methods:

• Fabrication and characterization of coupled quantum dot devices with one normal and one superconducting electrode.
• Low-temperature transport measurements to observe and quantify the Coulomb drag current.
• Theoretical analysis to understand the underlying physical mechanisms, including Andreev processes.

Main Results:

• Replacing a normal electrode with a superconducting one significantly boosts the Coulomb drag effect.
• At low temperatures and strong coupling, Coulomb drag is dominated by Andreev processes.
• The enhanced drag is robust against system parameter variations and controllable via gate voltage.
• A sign inversion of the drag current distinguishes this mechanism from single-particle contributions.

Conclusions:

• Superconducting electrodes offer a powerful route to enhance and control Coulomb drag in quantum dots.
• Andreev processes play a dominant role in the enhanced Coulomb drag under specific conditions.
• This controllable quantum effect has potential applications in novel electronic devices and sensors.