Efficient gate-tunable exciton–trion conversion in atomically thin WSe2 at sub-volt thresholds

Abstract

Atomically thin transition metal dichalcogenides exhibit significant potential for exciton-based optoelectronic and quantum applications owing to their strong light–matter interactions and tightly bound excitonic states. However, the practical realization of electrically programmable excitonic functionalities remains hindered by inefficient and power-intensive exciton–trion switching. Here, we demonstrate an energy-efficient exciton–trion switching strategy through integration of monolayer WSe2 with gold micropillar arrays. Micropillars with radii down to 1 µm induce strong localized strain in WSe2, significantly enhancing modulation efficiency and reducing the required gating voltage to as low as 0.6 V—approximately an order of magnitude lower than previously reported values. Periodic gating enables robust, reversible switching between neutral and trion exciton, supporting logic-like functionalities including binary encoding and signal inversion. Combined experiments and simulations reveal that this enhanced tunability arises from the synergistic interplay between strain localization and plasmonic field enhancement at the micropillar apex. These results establish an integrable, low-power approach for electrically programmable excitonic states, advancing integrated excitonic circuits based on two-dimensional semiconductors.