28 May 2024 | Feng Chen, Wei-Wei Luo, Wei Zhu, and D. N. Sheng
This study reports the observation of a robust non-Abelian even-denominator fractional Chern insulator (FCI) in twisted bilayer MoTe₂ at a fractional hole filling of 3/2. The research investigates the stability of an incompressible quantum Hall liquid in the half-filled Chern band of twisted MoTe₂ bilayers. Using a continuum model with parameters relevant to twisted MoTe₂, three nearly flat Chern bands with the same Chern number are identified. When the second moiré miniband is half-filled, non-Abelian states are observed through exact diagonalization calculations, including a stable six-fold ground state degeneracy, which is robust for larger lattice sizes and consistent with an even-denominator FCI state. Flux insertion simulations reveal a 1/2 quantized many-body Chern number, indicating topological order. The absence of sharp peaks in the ground state density structure factor suggests no charge density wave order. These findings suggest the potential realization of a non-Abelian state at zero magnetic field in twisted bilayer MoTe₂ at the fractional hole filling 3/2.
Transition metal dichalcogenide (TMD) moiré systems have attracted attention due to the discovery of emergent fractional Chern insulators (FCIs), which are zero magnetic field analogs of the fractional quantum Hall (FQH) effect. Theoretical studies demonstrate the engineering of topologically nontrivial flat bands in moiré systems and the emergence of FCI states such as the Laughlin states and other Jain sequence states. These results imply the resemblance of the quantum geometry of the moiré Chern bands to that of the lowest Landau level. This raises the question of whether the first excited Landau level physics with non-Abelian statistics can be realized in TMD moiré systems.
Recent experiments report quantum spin Hall plateaus in MoTe₂ at hole fillings ν = 2, 3, 4, 6 with a twist angle around θ ≈ 2.1°. The ν = 3 state remains time reversal invariant and supports helical edge modes with half-quantized edge conductance G = 3/2(e²/h), in contrast to previously observed valley polarized states. This ν = 3 state can be understood by examining possible phases in the second band. If the second moiré band is half-filled in each valley, it may produce a fractional quantum spin Hall insulator in the valley-decoupled limit. Together with the ν = 2 state from the filled lowest moiré band, it may explain the observed ν = 3 state.
The spontaneous time reversal symmetry breaking promoted by Coulomb interaction energy makes the higher moiré band a promising platform for discovering distinct non-Abelian FCIs. In the study of the half-filled first excited Landau level, leading topological ground state candidates include the non-Abelian Pfaffian, anti-PfThis study reports the observation of a robust non-Abelian even-denominator fractional Chern insulator (FCI) in twisted bilayer MoTe₂ at a fractional hole filling of 3/2. The research investigates the stability of an incompressible quantum Hall liquid in the half-filled Chern band of twisted MoTe₂ bilayers. Using a continuum model with parameters relevant to twisted MoTe₂, three nearly flat Chern bands with the same Chern number are identified. When the second moiré miniband is half-filled, non-Abelian states are observed through exact diagonalization calculations, including a stable six-fold ground state degeneracy, which is robust for larger lattice sizes and consistent with an even-denominator FCI state. Flux insertion simulations reveal a 1/2 quantized many-body Chern number, indicating topological order. The absence of sharp peaks in the ground state density structure factor suggests no charge density wave order. These findings suggest the potential realization of a non-Abelian state at zero magnetic field in twisted bilayer MoTe₂ at the fractional hole filling 3/2.
Transition metal dichalcogenide (TMD) moiré systems have attracted attention due to the discovery of emergent fractional Chern insulators (FCIs), which are zero magnetic field analogs of the fractional quantum Hall (FQH) effect. Theoretical studies demonstrate the engineering of topologically nontrivial flat bands in moiré systems and the emergence of FCI states such as the Laughlin states and other Jain sequence states. These results imply the resemblance of the quantum geometry of the moiré Chern bands to that of the lowest Landau level. This raises the question of whether the first excited Landau level physics with non-Abelian statistics can be realized in TMD moiré systems.
Recent experiments report quantum spin Hall plateaus in MoTe₂ at hole fillings ν = 2, 3, 4, 6 with a twist angle around θ ≈ 2.1°. The ν = 3 state remains time reversal invariant and supports helical edge modes with half-quantized edge conductance G = 3/2(e²/h), in contrast to previously observed valley polarized states. This ν = 3 state can be understood by examining possible phases in the second band. If the second moiré band is half-filled in each valley, it may produce a fractional quantum spin Hall insulator in the valley-decoupled limit. Together with the ν = 2 state from the filled lowest moiré band, it may explain the observed ν = 3 state.
The spontaneous time reversal symmetry breaking promoted by Coulomb interaction energy makes the higher moiré band a promising platform for discovering distinct non-Abelian FCIs. In the study of the half-filled first excited Landau level, leading topological ground state candidates include the non-Abelian Pfaffian, anti-Pf