Crossover from 2D metal to 3D Dirac semimetal in metallic PtTe2 films with local Rashba effect

TL;DR

This study investigates the electronic structure evolution of PtTe2 films from 2D metal to 3D Dirac semimetal, revealing a thickness-dependent transition and spin textures induced by Rashba effect, with implications for 2D topological materials.

Contribution

It provides the first systematic ARPES analysis of atomically thin PtTe2 films, demonstrating the transition from 2D metallic to 3D Dirac semimetal at specific thicknesses and uncovering Rashba-induced spin textures.

Findings

PtTe2 remains metallic down to 2 ML thickness.

Transition from 2D metal to 3D Dirac semimetal occurs at 4-6 ML.

Helical spin textures suggest local Rashba effect in PtTe2.

Abstract

PtTe2 and PtSe2 with trigonal structure have attracted extensive research interests since the discovery of type-II Dirac fermions in the bulk crystals. The evolution of the electronic structure from bulk 3D topological semimetal to 2D atomic thin films is an important scientific question. While a transition from 3D type-II Dirac semimetal in the bulk to 2D semiconductor in monolayer (ML) film has been reported for PtSe2, so far the evolution of electronic structure of atomically thin PtTe2 films still remains unexplored. Here we report a systematic angle-resolved photoemission spectroscopy (ARPES) study of the electronic structure of high quality PtTe2 films grown by molecular beam epitaxy with thickness from 2 ML to 6 ML. ARPES measurements show that PtTe2 films still remain metallic even down to 2 ML thickness, which is in sharp contrast to the semiconducting property of few layer PtSe2 film. Moreover, a transition from 2D metal to 3D type-II Dirac semimetal occurs at film thickness of 4-6 ML. In addition, Spin-ARPES measurements reveal helical spin textures induced by local Rashba effect in the bulk PtTe2 crystal, suggesting that similar hidden spin is also expected in few monolayer PtTe2 films. Our work reveals the transition from 2D metal to 3D topological semimetal and provides new opportunities for investigating metallic 2D films with local Rashba effect.