Negative Electron-electron Drag Between Narrow Quantum Hall Channels

TL;DR

This paper investigates Coulomb-induced electron drag between narrow quantum Hall channels, revealing that the drag can be negative or positive depending on the Landau level filling, with implications for understanding electron interactions in quantum Hall systems.

Contribution

It demonstrates the occurrence of negative electron-electron drag in quantum Hall channels and explains its dependence on Landau level filling factors, a novel insight into Coulomb interactions.

Findings

Negative drag occurs at fully occupied Landau levels.

Positive drag occurs at half-filled Landau levels.

Near-edge inter-LL transitions cause negative Coulomb drag.

Abstract

Momentum transfer due to Coulomb interaction between two parallel, two-dimensional, narrow, and spatially separated layers, when a current I_{drive} is driven through one layer, is studied in the presence of a perpendicular magnetic field B. The current induced in the drag layer, I_{drag}, is evaluated self-consistently with I_{drive} as a parameter. I_{drag} can be positive or negative depending on the value of the filling factor \nu of the highest occupied bulk Landau level (LL). For a fully occupied LL, I_{drag} is negative, i.e., it flows opposite to I_{drive}, whereas it is positive for a half-filled LL. When the circuit is opened in the drag layer, a voltage \Delta V_{drag} develops in it; it is negative for a half-filled LL and positive for a fully occupied LL. This positive \Delta V_{drag}, expressing a negative Coulomb drag, results from energetically favored near-edge inter-LL transitions that occur when the highest occupied bulk LL and the LL just above it become degenerate.