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1/4 is the new 1/2 when topology is intertwined with Mottness
Peizhi Mai1, Jinchao Zhao1, Benjamin E Feldman2,3,4
1Department of Physics and Institute of Condensed Matter Theory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
Nature Communications
|September 26, 2023
Summary
Topological states in non-interacting systems shift to quarter filling in the presence of strong interactions, forming a topological Mott insulator. This interaction-driven phenomenon allows for topological phases in gapless systems, explaining recent observations in moiré materials.
Area of Science:
- Condensed Matter Physics
- Quantum Materials
- Topological Phases of Matter
Background:
- Non-interacting systems exhibit topological bands at half-filling, leading to quantum anomalous Hall and spin Hall effects.
- Understanding the role of electron-electron interactions in topological phases is crucial for novel quantum phenomena.
Purpose of the Study:
- To investigate the impact of strong interactions on topological band structures.
- To identify the conditions under which topological states emerge in interacting systems.
- To explain recent experimental observations of quarter-filled topological effects in moiré systems.
Main Methods:
- Determinantal quantum Monte Carlo simulations.
- Analysis of an exactly solvable strongly interacting model.
Main Results:
- Topological states shift from half-filling to quarter-filling due to strong interactions, forming a topological Mott insulator.
- A peak in spin susceptibility suggests a possible ferromagnetic state at zero temperature.
- Interactions enable topological phases in gapless systems, provided interaction strength exceeds a critical value.
Conclusions:
- Strong electron-electron interactions are key to realizing topological phases at quarter-filling.
- The findings explain quarter-filled quantum anomalous Hall effects observed in moiré systems.
- Predicts the possibility of topological states in gapless, interacting dispersive band systems.
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