Searching for the fractional quantum Hall effect in graphite

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Understanding electronic properties of graphite is crucial for advanced electronic applications.
• Investigating graphite's behavior under extreme conditions, such as high magnetic fields and low temperatures, reveals fundamental physics.

Purpose of the Study:

• To investigate the electronic transport properties of highly oriented pyrolytic graphite (HOPG) under high pulsed magnetic fields.
• To explore the emergence of novel electronic phases and phenomena in graphite.

Main Methods:

• Measurements of basal plane longitudinal resistivity (rho(b)(B)) and Hall resistivity (rho(H)(B)) were conducted.
• Pulsed magnetic fields up to 50 Tesla were applied perpendicular to the graphene planes.
• Experiments were performed at cryogenic temperatures (1.5 K to 4.2 K).

Main Results:

• A sign change in Hall resistivity from electron-like to hole-like was observed above 30 Tesla.
• An enhancement in longitudinal resistivity was detected above 34 Tesla for the highest quality sample, indicating a possible phase transition.
• Well-defined plateaus in Hall resistivity were observed in the ultraquantum limit, suggesting fractional quantum Hall effect signatures.

Conclusions:

• The observed sign change in Hall resistivity indicates a significant modification of charge carrier behavior in graphite under high magnetic fields.
• The enhancement in longitudinal resistivity points towards field-induced charge density wave or Wigner crystallization.
• The plateaus in Hall resistivity provide compelling evidence for the fractional quantum Hall effect in graphite, opening new avenues for research.