Counter-propagating charge transport in the quantum Hall effect regime

Area of Science:

• Condensed Matter Physics
• Quantum Hall Effect
• 2D Electron Systems

Background:

• The quantum Hall effect typically exhibits downstream charge transport along sample edges.
• This downstream transport model is well-established for electrons and certain fractional quasiparticles.
• However, hole-conjugate states were theoretically predicted to host upstream charge modes, a phenomenon yet to be experimentally confirmed.

Purpose of the Study:

• To investigate the transport properties of quasiparticles in hole-conjugate states.
• To experimentally verify the existence of upstream charge currents in the quantum Hall regime.
• To explore the role of spin polarization in these exotic transport phenomena.

Main Methods:

• Fabrication and characterization of GaAs-AlGaAs heterostructures.
• Measurement of charge transport in 2D electron gases under perpendicular magnetic fields.
• Analysis of spin-polarized and spin-unpolarized v = 2/3 hole-like states.

Main Results:

• A significant upstream charge current was detected at short propagation distances.
• This upstream current was observed specifically in the spin-unpolarized state of the v = 2/3 hole-like system.
• The findings contradict the prevailing notion of exclusively downstream transport in the quantum Hall regime.

Conclusions:

• The experimental observation of upstream charge current in hole-conjugate states validates theoretical predictions.
• This discovery challenges the established understanding of charge transport in the quantum Hall effect.
• The results highlight the complex nature of quasiparticle behavior and the influence of spin in these systems.