Spintronic Quantum Phase Transition in a $Graphene/Pb_{0.24}Sn_{0.76}Te$ Heterostructure with Giant Rashba Spin-Orbit Coupling

TL;DR

This study investigates a heterostructure of graphene and Pb0.24Sn0.76Te, revealing a spintronic quantum phase transition driven by a giant Rashba effect, with observable changes in spin transport properties around 40 K.

Contribution

It demonstrates a spintronic quantum phase transition in a graphene/Pb0.24Sn0.76Te heterostructure caused by a giant Rashba spin-orbit coupling, confirmed by both experiments and density functional theory.

Findings

Spin-momentum locking observed at low temperatures

Transition to regular spin channel transport at ~40 K

High spin relaxation time of 2.18 ns

Abstract

Mechanical stacking of two dissimilar materials often has surprising consequences for heterostructure behavior. In particular, a two-dimensional electron gas (2DEG) is formed in the heterostructure of the topological crystalline insulator Pb0.24Sn0.76Te and graphene due to contact of a polar with a nonpolar surface and the resulting changes in electronic structure needed to avoid polar catastrophe. We study the spintronic properties of this heterostructure with non-local spin valve devices. We observe spin-momentum locking at lower temperatures that transitions to regular spin channel transport only at ~40 K. Hanle spin precession measurements show a spin relaxation time as high as 2.18 ns. Density functional theory calculations confirm that the spin-momentum locking is due to a giant Rashba effect in the material and that the phase transition is a Lifshitz transition. The theoretically predicted Lifshitz transition is further evident in the phase transition-like behavior in the Land\'e g-factor and spin relaxation time.