Gate Tunable Giant Helical In-plane Exciton Dipole in Flat Chern Bands
ORAL
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.
*This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-SC0025327. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 using NERSC award BES-ERCAP0032546 and BES-ERCAP0033256.This work was also facilitated through the use of advanced computational, storage, and networking infrastructure provided by the Hyak supercomputer system and funded by the University of Washington Molecular Engineering Materials Center at the University of Washington (DMR-2308979).
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Presenters
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Kai-Jie Yang
- University of Washington
- The univeristy of Washington - Seattle