Valley-Selective Landau-Zener Oscillations in Semi-Dirac p-n Junctions

TL;DR

This paper investigates how electron tunneling in semi-Dirac p-n junctions varies with orientation, revealing valley-selective transport and non-monotonic current-voltage behavior due to anisotropic band dispersion.

Contribution

It introduces the study of valley-selective Landau-Zener oscillations in semi-Dirac materials and shows how junction orientation influences tunneling and transport properties.

Findings

Tunneling depends on barrier orientation relative to crystal axes.

Current-voltage characteristics can be non-monotonic, including negative differential conductance.

Valley-selective transport can be engineered in multi-valley systems.

Abstract

We study transport across p-n junctions of gapped two-dimensional semi-Dirac materials: nodal semimetals whose energy bands disperse quadratically and linearly along distinct crystal axes. The resulting electronic properties --- relevant to materials such as TiO$_2$/VO$_2$ multilayers and $\alpha$-(BEDT-TTF)$_2$I$_3$ salts --- continuously interpolate between those of mono- and bi-layer graphene as a function of propagation angle. We demonstrate that tunneling across the junction depends on the orientation of the tunnel barrier relative to the crystalline axes, leading to strongly non-monotonic current-voltage characteristics, including negative differential conductance in some regimes. In multi-valley systems these features provide a natural route to engineering valley-selective transport.