Engineering Quantum Confinement in Semiconducting van der Waals   Heterostructure
  Spatial confinement and manipulation of charged carriers in semiconducting nanostructures are essential for realizing quantum electronic devices. Gate-defined nanostructures made of two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDCs) have the potential to add a unique additional control of quantum degrees of freedom owing to valley-spin locking of confined carriers near the band edges. However, due to prevailing inhomogeneities in the conducting channels, it has been difficult to realize quantum confinement in 2D TMDCs with well-controlled tunnel-coupling strength. Here we demonstrate quantum transport in lateral gate-defined 2D electron quantum dots formed in atomically thin TMDC heterostructures. Utilizing micro-fabricated local contact gates, encapsulation in 2D dielectrics and light illumination at low temperatures, we show that the quality of TMDC 2D electron gases (2DEGs) can be improved, rendering them suitable for mesoscopic quantum transport measurements. We observe quantized conductance in quantum point contact (QPC) channels controlled by gate-tunable confinement. We also demonstrate single electron transport in TMDC quantum dots (QD) with tunable tunnel-coupling. Our observation holds promise for the quantum manipulation of spin and valley degrees of freedom in engineered TMDC nanostructures, enabling versatile 2D quantum electronic devices. 
Ke Wang, Takashi Taniguchi, Kenji Watanabe, Philip Kim
cond-mat.mes-hall