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Quantum parity Hall effect in Bernal-stacked trilayer graphene
Petr Stepanov1, Yafis Barlas2, Shi Che1
1Department of Physics and Astronomy, The Ohio State University, Columbus, OH 43210.
Researchers discovered the quantum parity Hall effect in trilayer graphene, where boundary channels are defined by mirror symmetry. This reveals a novel topological phase sensitive to interactions and controllable by gate voltage.
Area of Science:
- Condensed Matter Physics
- Quantum Hall Effect
- Materials Science
Background:
- The quantum Hall effect (QHE) has been extended to include spin and valley transport using polarized boundary states.
- Trilayer graphene (TLG) offers a unique platform for exploring novel quantum phenomena due to its distinct electronic structure.
Purpose of the Study:
- To report a new class of quantum Hall effect, the quantum parity Hall (QPH) effect, in Bernal- or ABA-stacked TLG.
- To investigate the role of mirror reflection symmetry in defining boundary channels within this QPH effect.
- To understand the influence of exchange interactions and Coulomb forces on the topological phase transitions.
Main Methods:
- Experimental observation of longitudinal conductance in TLG under varying perpendicular magnetic fields.
- Analysis of edge channel behavior, including quantization and spin polarization.
- Theoretical interpretation involving Landau level crossings and symmetry protection.
Main Results:
- Quantized longitudinal conductance of 2e²/h observed at low magnetic fields, indicating four edge channels.
- Conductance transitions to e²/h and then to zero with increasing magnetic field, signifying spin-polarized counterpropagating edge states.
- Evidence of level crossings between even- and odd-parity bulk Landau levels driven by exchange interactions.
Conclusions:
- Demonstration of the quantum parity Hall effect in trilayer graphene, characterized by parity-distinguished boundary channels.
- Identification of a tunable topological phase protected by gate-controlled symmetry and influenced by Coulomb interactions.
- The observed phenomena are attributed to exchange interactions favoring different ground states (ordinary insulator or spin-polarized) depending on magnetic field strength and Zeeman energy.
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