Tunable valley filtering in dynamically strained $\alpha$-$\mathcal{T}_3$ lattices

TL;DR

This paper proposes a method to create tunable valley filters in $ ext{alpha-} ext{T}_3$ lattices using dynamic strain and oscillating pseudomagnetic fields, enabling control over valley polarization for potential device applications.

Contribution

It introduces a dynamic strain approach to engineer tunable valley filtering in $ ext{alpha-} ext{T}_3$ lattices, extending static capabilities with time-dependent control.

Findings

Identification of energy regimes with high valley polarization

Demonstration of control over valley states via driving frequency

Analysis of spatial distributions of local density of states and current density

Abstract

Mechanical deformations in $\alpha$-$\mathcal{T}_3$ lattices induce local pseudomagnetic fields of opposite directionality for different valleys. When this strain is equipped with a dynamical drive, it generates a complementary valley-asymmetric pseudoelectric field which is expected to accelerate electrons. We propose that by combining these effects by a time-dependent nonuniform strain, tunable valley filtering devices can be engineered that extend beyond the static capabilities. We demonstrate this by implementing an oscillating Gaussian bump centered in a four-terminal Hall bar $\alpha$-$\mathcal{T}_3$ setup and calculating the induced pseudoelectromagnetic fields analytically. Within a recursive Floquet Green-function scheme, we determine the time-averaged transmission and valley polarization, as well as the spatial distributions of the local density of states and current density. As a result of the periodic drive, we detect novel energy regimes with highly valley-polarized transmission, depending on $\alpha$. Analyzing the spatial profiles of the time-averaged local density of states and current density we can relate these regimes to the pseudoelectromagnetic fields in the setup.By means of the driving frequency, we can manipulate the valley-polarized states, which might be advantageous for future device applications.