Hubbard model physics in transition metal dichalcogenide moiré bands (1804.03151v3)

Abstract: Flexible long period moir\' e superlattices form in two-dimensional van der Waals crystals containing layers that differ slightly in lattice constant or orientation. In this Letter we show theoretically that isolated flat moir\' e bands described by generalized triangular lattice Hubbard models are present in twisted transition metal dichalcogenide heterobilayers. The hopping and interaction strength parameters of the Hubbard model can be tuned by varying the twist angle and the three-dimensional dielectric environment. When the flat moir\'e bands are partially filled, candidate many-body ground states at some special filling factors include spin-liquid states, quantum anomalous Hall insulators and chiral $d$-wave superconductors.

• The paper introduces a generalized Hubbard model on TMD moiré superlattices, revealing flat bands with tunable hopping and interaction strengths.
• The paper predicts exotic quantum phases, including spin liquids, quantum anomalous Hall states, and chiral d-wave superconductors, by varying the twist angle and dielectric environment.
• The paper emphasizes the experimental potential of TMD heterobilayers as a platform for investigating strongly correlated electron systems and phase transitions.

Overview of "Hubbard Model Physics in Transition Metal Dichalcogenide Moiré Bands"

This paper presents an investigation into the application of the Hubbard model to twisted heterobilayers composed of transition metal dichalcogenides (TMDs). The authors, Wu et al., propose the use of these TMD moiré superlattices to explore complex many-body quantum phases due to their unique electronic properties.

Main Contributions

The paper focuses on the electronic properties of moiré superlattices that form when two-dimensional van der Waals crystals with slightly mismatched lattice constants or orientations are overlaid. These moiré patterns result in isolated and flat electronic bands that can be well-described by a generalized triangular lattice Hubbard model. The tunability of key parameters in these models, such as hopping and interaction strengths, is facilitated by adjusting the twist angle and the surrounding dielectric environment.

Key theoretical predictions include the existence of exotic states such as spin liquids, quantum anomalous Hall insulators, and chiral d-wave superconductors. The paper identifies that in the regime where the moiré bands are partially filled, these systems exhibit strong electron-electron correlations, influenced by the tuning of model parameters.

Theoretical and Practical Implications

1. New Platform for Studying Strongly Correlated Electrons:
   • The paper highlights the potential of TMD heterobilayers as experimental platforms for simulating strongly correlated electron systems. These systems traditionally offer challenges due to their complex many-body interactions.
2. Tunable Quantum Phases:
   • By controlling the twist angle, the dielectric environment, and applying external fields, it is possible to explore various quantum phases, which are not easily accessible in traditional materials. This tunability provides a robust avenue for exploring phase transitions and critical phenomena in two-dimensional systems.
3. Prospects for Realizing Spin-Liquid States:
   • The proposed systems are shown to potentially manifest spin-liquid states in certain configurations, particularly when the bands are close to half-filling. This provides a solid-state platform for studying exotic magnetic phases that are of significant theoretical interest.

Future Directions

The paper opens several avenues for future research. Experimentally, the verification of the predicted quantum phases and the detailed paper of their properties will be crucial steps. Additionally, further exploration into different material systems and configurations could enhance the understanding of the Hubbard model in two-dimensional systems. The development of experimental techniques capable of probing these states, particularly at low temperatures, is also essential.

In terms of theory, further refinements in the modeling of interactions in such highly controlled environments could lead to even more accurate predictions and a deeper understanding of the phases present in these systems. The exploration of heterobilayers with different material combinations or the introduction of additional tuning parameters, such as strain, might yield new insights and potential applications.

Conclusion

This paper provides a significant contribution to the paper of moiré superlattices in TMDs, effectively bridging theoretical models and experimental realizations. The insights gained from this research have broad implications for the field of condensed matter physics and hold promise for advancing the understanding and control of quantum materials with strongly correlated electronic properties.