Engineering a Spin-Orbit Bandgap in Graphene-Tellurium Heterostructures

TL;DR

This study demonstrates the creation of a sizable spin-orbit bandgap in graphene via tellurium intercalation, revealing tunable electronic properties and a potential quantum spin Hall phase in graphene heterostructures.

Contribution

It introduces a novel method of intercalating tellurium in graphene heterostructures to induce and tune a significant spin-orbit bandgap at room temperature.

Findings

A 240 meV bandgap opens at the Dirac point.

Te induces n-doping and allows energy tuning of the Dirac point.

Evidence suggests a quantum spin Hall phase with chiral spin texture.

Abstract

Intensive research has focused on harnessing the potential of graphene for electronic, optoelectronic, and spintronic devices by generating a bandgap at the Dirac point and enhancing the spin-orbit interaction in the graphene layer. Proximity to heavy p elements is a promising approach; however, their interaction in graphene heterostructures has not been as intensively studied as that of ferromagnetic, noble, or heavy d metals, neither as interlayers nor as substrates. In this study, the effective intercalation of Te atoms in a graphene on Ir(111) heterostructure is achieved. Combining techniques such as low energy electron diffraction and scanning tunneling microscopy, the structural evolution of the system as a function of the Te coverage is elucidated, uncovering up to two distinct phases. The presented angle-resolved photoemission spectroscopy analysis reveals the emergence of a bandgap of about 240 meV in the Dirac cone at room temperature, which preserves its characteristic linear dispersion. Furthermore, a pronounced n-doping effect induced by Te in the heterostructure is also observed, and remarkably the possibility of tuning the Dirac point energy towards the Fermi level by reducing the Te coverage while maintaining the open bandgap is demonstrated. Spin-resolved measurements unveil a non-planar chiral spin texture with significant splitting values for both in-plane and out-of-plane spin components. These experimental findings are consistent with the development of a quantum spin Hall phase, where a Te-enhanced intrinsic spin orbit coupling in graphene surpasses the Rashba one and promotes the opening of the spin-orbit bandgap.