Microscopic Origin of the Valley Hall Effect in Transition Metal Dichalcogenides Revealed by Wavelength Dependent Mapping

Abstract

The band structure of many semiconducting monolayer transition metal dichalcogenides (TMDs) possesses two degenerate valleys, with equal and opposite Berry curvature. It has been predicted that, when illuminated with circularly polarized light, interband transitions generate an unbalanced non-equilibrium population of electrons and holes in these valleys, resulting in a finite Hall voltage at zero magnetic field when a current flows through the system. This is the so-called valley Hall effect that has recently been observed experimentally. Here, we show that this effect is mediated by photo-generated neutral excitons and charged trions, and not by inter-band transitions generating independent electrons and holes. We further demonstrate an experimental strategy, based on wavelength dependent spatial mapping of the Hall voltage, which allows the exciton and trion contributions to the valley Hall effect to be discriminated in the measurement. These results represent a significant step forward in our understanding of the microscopic origin of photo-induced valley Hall effect in semiconducting transition metal dichalcogenides, and demonstrate experimentally that composite quasi-particles, such as trions, can also possess a finite Berry curvature.

accepted for publication in Nano Letters

References in corpus (10)

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• The Valley Hall Effect in MoS2 Transistors
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Cited by in corpus (12)

• Thickness dependence of work function, ionization energy, and electron affinity of Mo and W dichalcogenides from DFT and GW calculations
• Tunable and giant valley-selective Hall effect in gapped bilayer graphene
• Valley Acoustoelectric Effect
• Valley Degree of Freedom in Two-Dimensional van der Waals Materials
• Kapitza-resistance-like exciton dynamics in atomically flat MoSe${}_2$-WSe${}_2$ lateral heterojunction
• Valley contrasting bulk photovoltaic effect in antiferromagnetic MnPSe${}_3$ monolayer
• Scanning Tunneling Microscopy of an Air Sensitive Dichalcogenide Through an Encapsulating Layer
• Valley and spin accumulation in ballistic and hydrodynamic channels
• Photoinduced Anomalous Supercurrent Hall Effect
• Inheritance of the exciton geometric structure from Bloch electrons in two-dimensional layered semiconductors
• Twistronics and moiré superlattice physics in 2D transition metal dichalcogenides
• Spin Pumping into two-dimensional systems