Ambipolar degeneracy breaking via surface acoustic wave-driven bidirectional carrier transport in optically reconfigurable MoTe₂/h-BN heterostructure

Two-dimensional (2D) materials hold immense potential for next-generation information devices due to their ambipolar transport and tunable electronic states. However, conventional electric-field-driven architectures suffer from inherent carrier-type degeneracy: Electrons and holes generate unidirectional currents, leading to ambiguous state overlaps in multi-level operation. Here, we demonstrate that surface acoustic waves (SAWs) break this symmetry in optically reconfigurable MoTe₂/h-BN heterostructures. SAWs induce type-II band modulation in the heterostructure and spatially separate electrons and holes into distinct valleys, enabling bidirectional acoustoelectric currents, whose polarity reverses with carrier type, controlled dynamically via ultraviolet (UV) illumination and gating. Leveraging this mechanism, we realize an 8-state memory device where SAW-driven readout currents changed between positive and negative polarities, achieving enhanced inter-state differentiation compared to voltage-read schemes. For synaptic applications, SAW-driven weight updates in n- and p-type regimes produce anti-symmetric conductance trajectories, eliminating state collisions observed in electric-field-driven counterparts. This work pioneers acoustic wave manipulation of ambipolar transport, offering transformative strategies for degeneracy-free, high-precision neuromorphic electronics.