Gate Tunable Giant Helical In-plane Exciton Dipole in Flat Chern Bands
Oral-In-person
Abstract
The presence of flat Chern bands in moir\'e materials offers an opportunity to generalize the Landau level physics into the lattice systems without magnetic field.
In this work, we study the valley exciton of twisted MoTe$_2$ formed between two flat valence minibands with valley Chern number $C_K=1$.
At zero displacement field, we discover that the lowest-energy exciton forms in-plane helical dipole texture in the momentum space, with the dipole perpendicular to the center-of-mass momentum near $\gamma$.
The dipole originates in the Berry curvature inherited from electron and hole bands and reaches the moir\'e unit cell length scale of nanometers.
Increasing the displacement field results in a indirect-to-direct bandgap transition, tunes the dipole magnitude, and reverses its helicity through the envelop function change from the Frankel type to Wannier type in terms of the moir\'e unit cell.
The dipole texture also leads to gate tunable exciton drift velocities in response to the uniform electrical field.
Our work shows the tMoTe$_2$ as an appealing electrically tunable platform in study exciton dipole physics.
propose experimental measurement. new physics for THz optical systems.
In this work, we study the valley exciton of twisted MoTe$_2$ formed between two flat valence minibands with valley Chern number $C_K=1$.
At zero displacement field, we discover that the lowest-energy exciton forms in-plane helical dipole texture in the momentum space, with the dipole perpendicular to the center-of-mass momentum near $\gamma$.
The dipole originates in the Berry curvature inherited from electron and hole bands and reaches the moir\'e unit cell length scale of nanometers.
Increasing the displacement field results in a indirect-to-direct bandgap transition, tunes the dipole magnitude, and reverses its helicity through the envelop function change from the Frankel type to Wannier type in terms of the moir\'e unit cell.
The dipole texture also leads to gate tunable exciton drift velocities in response to the uniform electrical field.
Our work shows the tMoTe$_2$ as an appealing electrically tunable platform in study exciton dipole physics.
propose experimental measurement. new physics for THz optical systems.
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Presenters
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Kai-Jie Yang
- The univeristy of Washington - Seattle