Valley-selective transport in 2D ferrovalley semiconductors via interfacial coupling and external fields

Harnessing the intrinsic valley degree of freedom for carrier injection is pivotal for low-power valleytronic logic and nonvolatile memory. However, designing efficient, selective injection at high-quality metal/ferrovalley-semiconductor (MFVS) interfaces remains a critical challenge. Herein, we propose a valley-selective contact strategy to achieve highly efficient carrier injection in MFVS junctions. Our investigation into interface physics across diverse electrodes reveals a trade-off: while strong-coupling contacts lower tunneling barriers, metal-induced gap states significantly degrade intrinsic valley properties. We further demonstrate that strain engineering induced by lattice mismatch not only modifies the magnitude of valley splitting but also induces a complete reversal of valley polarization. Notably, a vertical electric field enables precise modulation of the interfacial band alignment, shifting the K and K' valleys relative to the Fermi level and thereby allowing electrical switching among overall-valley Schottky, single-valley Ohmic, and overall-valley Ohmic contact regimes, leading to highly selective valley transport. Based on these mechanisms, we develop a high-performance dual-gate device model verifying electrically controlled carrier injection under ideal transport conditions. This work establishes a robust design framework for integrating valleytronic functionalities, paving the way for advanced valley-based electronics.