Coulomb drag in coherent mesoscopic systems

Area of Science:

• Condensed matter physics
• Mesoscopic physics
• Quantum transport

Background:

• Coulomb drag measures interactions between nearby electronic systems.
• Understanding drag in mesoscopic systems is crucial for quantum electronics.
• Existing theories often limited to specific regimes (e.g., purely ballistic or disordered).

Purpose of the Study:

• To present a unified theory for Coulomb drag in mesoscopic systems.
• To extend the understanding of Coulomb drag to include localized states.
• To investigate the behavior of Coulomb drag in both 2D chaotic and 1D disordered systems.

Main Methods:

• Developed a theoretical formalism based on scattering matrices and wave functions.
• Applicable to both ballistic and disordered mesoscopic systems.
• Utilized analytic methods (e.g., random matrix theory) and numerical simulations.

Main Results:

• Coulomb drag is sensitive to localized electronic states, unobservable by standard transport measurements.
• In chaotic 2D systems, the average Coulomb drag is zero, but its variance is non-zero.
• Disordered 1D wires exhibit a finite Coulomb drag with significant variance, potentially leading to induced current sign changes.

Conclusions:

• The presented theory provides a comprehensive framework for Coulomb drag in mesoscopic systems.
• Coulomb drag can serve as a sensitive probe for localized states.
• The distinct behaviors in 2D and 1D systems highlight the importance of dimensionality and disorder in Coulomb drag phenomena.