Inhibiting Klein tunneling in graphene p-n junction without an external magnetic field

TL;DR

This study demonstrates that organic molecule islands on graphene can create a magnetic barrier that inhibits Klein tunneling without external magnetic fields, due to spontaneous ferromagnetic order induced by doping.

Contribution

It reveals a novel method to inhibit Klein tunneling in graphene using organic molecular islands and doping-induced ferromagnetism, avoiding external magnetic fields.

Findings

Densely packed F4TCNQ islands induce p-n junctions in graphene.

Doping leads to spontaneous ferromagnetic order in the molecular island.

Magnetic barriers of around 10 mT can inhibit Klein tunneling.

Abstract

We study by first-principles calculations a densely packed island of organic molecules (F4TCNQ) adsorbed on graphene. We find that with electron doping the island naturally forms a p-n junction in the graphene sheet. For example, a doping level of ~ 3 * 10^{13} electrons per cm^2 results in a p-n junction with 800 meV electrostatic potential barrier. Unlike in a conventional p-n junction in graphene, in the case of the junction formed by an adsorbed organic molecular island we expect that the Klein tunneling is inhibited, even without an applied external magnetic field. Here Klein tunneling is inhibited by the ferromagnetic order that spontaneously occurs in the molecular island upon doping. We estimate that the magnetic barrier in the graphene sheet is around 10 mT.