Electrostatic Modulation of Valley Polarization via a Single-Contact Method in Monolayer WSe₂ for Valleytronic Devices

The emerging field of valleytronics has sparked significant interest in controlling valley pseudospin in monolayer transition metal dichalcogenides (ML-TMDs). However, maintaining valley polarization (VP) is challenging at high temperatures and during off-resonance excitation. In this study, we introduce an electrostatically tunable single-contact device based on ML-WSe2, which demonstrates enhanced photoluminescence intensity and VP modulation under off-resonance conditions compared to conventional back-gate methods. Our findings could be illustrated by an electrostatic doping model, which suggests stronger and more uniform doping at the device center. Furthermore, a clear controllability of trion VP switching is also demonstrated over a wide temperature range. The efficient VP control in ML-TMD via the single-contact design enables future applications in valleytronics and optoelectronics.