Valley and spin pump by scattering at non-magnetic disorders

Abstract

In solid, the crystalline structure can endow electron an internal degree of freedom known as valley, which characterizes the degenerate energy minima in momentum space. The recent success in optical pumping of valley polarization in 2D transition metal dichalcogenides (TMDs) has greatly promoted the concept of valley-based informatics and electronics. However, between the demonstrated valley polarization of transient electron-hole pair excitations and practical valleytronic operations, there exist obvious gaps to fill, among which is the valley pump of long-lived charge carriers. Here we discover that the quested valley pump of electrons or holes can be realized simply by scattering at the ubiquitous nonmagnetic disorders, not relying on any specific material property. The mechanism is rooted in the nature of valley as a momentum space index: the intervalley backscattering in general has valley contrasted rate due to the distinct momentum transfers, causing a net transfer of population from one valley to another. As examples, we numerically demonstrate the sizable valley pump effects driven by charge current in nanoribbons of monolayer TMDs, where the spin-orbit scattering by non-magnetic disorders also realizes spin pump for the spin-valley locked holes. Our finding points to an unexpected new opportunity towards valley-spintronics, turning disorders from a deleterious factor to a resource of valley and spin polarization.

14 pages, 3 figures

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Cited by in corpus (13)

• Dissipationless Layertronics in Axion Insulator $\mathrm{MnB}{\mathrm{i}}_2\mathrm{T}{\mathrm{e}}_4$
• Symmetry-forbidden intervalley scattering by atomic defects in monolayer transition-metal dichalcogenides
• Floquet Valley-Polarized Quantum Anomalous Hall State in Nonmagnetic Heterobilayers
• Perfect valley filter based on topological phase in disordered $\mathrm{Sb}$ Monolayer Heterostructure
• Valley-selective Klein tunneling through superlattice barrier in graphene
• Electrical valley filtering in transition metal dichalcogenides
• Realization of valley-spin polarized current via parametric pump in monolayer $\mathrm{Mo}{\mathrm{S}}_2$
• Valley polarization and valleyresistance in monolayer transition metal dichalcogenides superlattice
• Valley-resolved Fano resonance in monolayer transition metal dichalcogenides nanoribbons with attached stubs
• Valley filters, accumulators, and switches induced in graphene quantum dots by lines of adsorbed hydrogen atoms
• Switchable valley functionalities of an $n-n^{-}-n$ junction in 2D semiconductors
• Spin-polarized transport properties in magnetic moiré superlattices
• Valley Gapless Semiconductor: Models and Applications