Quantum Hall effect near the charge neutrality point in a two-dimensional electron-hole system

Area of Science:

• Condensed matter physics
• Quantum phenomena
• Semiconductor heterostructures

Background:

• HgTe-based quantum wells are platforms for studying complex electronic behaviors.
• Understanding electron-hole interactions in confined systems is crucial for novel electronic devices.
• The charge neutrality point (CNP) in such systems presents unique transport characteristics.

Purpose of the Study:

• To investigate the transport properties of HgTe quantum wells with coexisting electrons and holes under a magnetic field.
• To elucidate the mechanism behind the observed transport phenomena at the charge neutrality point.
• To explore the role of electron-hole interactions and emergent states in these systems.

Main Methods:

• Experimental measurement of resistance and Hall resistivity in HgTe-based quantum wells.
• Application of a magnetic field (B) to tune the system's electronic properties.
• Analysis of conductivity tensors (Hall conductivity sigma(xy) and diagonal conductivity sigma(xx)) as a function of magnetic field and Landau level filling factors.

Main Results:

• At the charge neutrality point (CNP), resistance significantly increased with magnetic field B.
• Hall resistivity approached zero, forming a plateau in Hall conductivity (sigma(xy) ≈ 0).
• A minimum in diagonal conductivity (sigma(xx)) was observed at nu = nu(p) - nu(n) = 0, consistent with electron-hole "snake states".

Conclusions:

• The transport at the CNP is dominated by electron-hole "snake states" propagating along the nu = 0 lines.
• Observed phenomena share similarities with the quantum Hall effect in graphene and transport in random magnetic fields.
• These findings offer insights into exotic electronic states in correlated electron-hole systems.