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Unconventional Topological Phase Transition in Two-Dimensional Systems with Space-Time Inversion Symmetry
Junyeong Ahn1,2,3, Bohm-Jung Yang1,2,3
1Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea.
Physical Review Letters
|April 29, 2017
Summary
A new topological phase transition pathway is discovered in 2D systems with space-time inversion symmetry. This transition is mediated by a stable 2D Weyl semimetal phase, unlike direct transitions in simpler systems.
Area of Science:
- Condensed Matter Physics
- Topological Materials
- Quantum Phenomena
Background:
- Topological phase transitions typically occur directly between insulating states in time-reversal invariant systems.
- Two-dimensional (2D) systems with combined time-reversal and twofold rotation symmetries possess unique properties due to space-time inversion symmetry.
Purpose of the Study:
- To investigate the nature of topological phase transitions in 2D systems with both time-reversal and twofold rotation symmetries.
- To identify the mediating phase during transitions between normal and quantum spin Hall insulators under these specific symmetries.
Main Methods:
- Theoretical analysis of topological phase transitions.
- Investigation of the role of space-time inversion symmetry in Berry phase quantization.
- Study of Weyl point creation, annihilation, and their impact on topological invariants.
Main Results:
- A stable 2D Weyl semimetal phase emerges as a mediator in topological phase transitions between normal and quantum spin Hall insulators.
- Space-time inversion symmetry ensures Berry phase quantization around 2D Weyl points, even with strong spin-orbit coupling.
- HgTe/CdTe quantum wells and few-layer black phosphorus under electric fields are identified as potential experimental platforms.
Conclusions:
- Topological phase transitions in systems with space-time inversion symmetry are unconventional, proceeding via an emergent 2D Weyl semimetal phase.
- This mechanism offers new pathways for realizing and controlling topological states in 2D materials.
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