Electrical valley filtering in transition metal dichalcogenides

TL;DR

This paper explores electrical valley filtering in transition metal dichalcogenides using potential barriers, demonstrating how tunneling properties depend on barrier parameters and orientation, and achieving up to 10% valley polarization.

Contribution

It introduces a combined analytic and numerical approach to analyze valley-dependent tunneling, highlighting the roles of band structure warping and valley-orbit interaction.

Findings

Valley polarization increases with barrier width and height.

Band structure warping and valley-orbit interaction influence tunneling.

Achieves approximately 10% valley polarization at certain transmission levels.

Abstract

This work investigates the feasibility of electrical valley filtering for holes in transition metal dichalcogenides. We look specifically into the scheme that utilizes a potential barrier to produce valley-dependent tunneling rates, and perform the study with both a k.p based analytic method and a recursive Green's function based numerical method. The study yields the transmission coefficient as a function of incident energy and transverse wave vector, for holes going through lateral quantum barriers oriented in either armchair or zigzag directions, in both homogeneous and heterogeneous systems. The main findings are the following: 1) the tunneling current valley polarization increases with increasing barrier width or height, 2) both the valley-orbit interaction and band structure warping contribute to valley-dependent tunneling, with the former contribution being manifest in structures with asymmetric potential barriers, and the latter being orientation-dependent and reaching maximum for transmission in the armchair direction, and 3) for transmission ~ 0.1, a tunneling current valley polarization of the order of 10% can be achieved.