Valley filtering in strain-induced $\alpha$-$\mathcal{T}_3$ quantum dots

TL;DR

This paper investigates how strain-induced quantum dots in an $ ext{alpha}$-$ ext{T}_3$ lattice can generate valley-polarized currents, revealing different transport regimes and the role of local symmetry breaking in valley filtering.

Contribution

It introduces a method to achieve valley filtering in $ ext{alpha}$-$ ext{T}_3$ quantum dots using strain-induced pseudomagnetic fields and analyzes the resulting transport phenomena and local density distributions.

Findings

Valley filtering depends on quantum dot geometry and strain parameters.

Conductance resonances are linked to pseudo-Landau levels.

Local symmetry breaking influences sublattice filtering.

Abstract

We test the valley-filtering capabilities of a quantum dot inscribed by locally straining an $\alpha$-$\mathcal{T}_3$ lattice. Specifically, we consider an out-of-plane Gaussian bump in the center of a four-terminal configuration and calculate the generated pseudomagnetic field having an opposite direction for electrons originating from different valleys, the resulting valley-polarized currents, and the conductance between the injector and collector situated opposite one another. Depending on the quantum dot's width and width-to-height ratio, we detect different transport regimes with and without valley filtering for both the $\alpha$-$\mathcal{T}_3$ and dice lattice structures. In addition, we analyze the essence of the conductance resonances with a high valley polarization in terms of related (pseudo-) Landau levels, the spatial distribution of the local density of states, and the local current densities. The observed local charge and current density patterns reflect the local inversion symmetry breaking by the strain, besides the global inversion symmetry breaking due to the scaling parameter $\alpha$. By this way we can also filter out different sublattices.