Anisotropic transport of normal metal-barrier-normal metal junctions in monolayer phosphorene

TL;DR

This paper investigates anisotropic electron transport in monolayer phosphorene with potential barriers, revealing unique collimation and tunneling behaviors of massive Dirac electrons, and contrasts these with graphene and Schrödinger electrons.

Contribution

It provides a detailed analysis of transport properties in phosphorene, highlighting its potential for studying Klein paradox and anisotropic tunneling, with analytical bounds for conductance decay.

Findings

Transport along armchair edge is qualitatively different from graphene and topological insulators.

Achieves collimated quasiparticle motion enabling Klein paradox studies.

Conductance behavior transitions from oscillatory to decaying with barrier width.

Abstract

We study transport properties of a phosphorene monolayer in the presence of single and multiple potential barriers of height $U_0$ and width $d$, using both continuum and microscopic lattice models, and show that the nature of electron transport along its armchair edge ($x$ direction) is qualitatively different from its counterpart in both conventional two-dimensional electron gas with Schr\"odinger-like quasiparticles and graphene or surfaces of topological insulators hosting massless Dirac quasiparticles. We show that the transport, mediated by massive Dirac electrons, allows one to achieve collimated quasiparticle motion along $x$ and thus makes monolayer phosphorene an ideal experimental platform for studying Klein paradox. We study the dependence of the tunneling conductance $G \equiv G_{xx}$ as a function of $d$ and $U_0$, and demonstrate that for a given applied voltage $V$ its behavior changes from oscillatory to decaying function of $d$ for a range of $U_0$ with finite non-zero upper and lower bounds, and provide analytical expression for these bounds within which $G$ decays with $d$. We contrast such behavior of $G$ with that of massless Dirac electrons in graphene and also with that along the zigzag edge ($y$ direction) in phosphorene where the quasiparticles obey an effective Schr\"odinger equation at low energy. We also study transport through multiple barriers along $x$ and demonstrate that these properties hold for transport through multiple barrier as well. Finally, we suggest concrete experiments which may verify our theoretical predictions.