Transition metal dichalcogenides (TMDCs) formed by group 10 metals (e.g. PtSe2, PtTe2) have emerged as important materials with intriguing properties discovered both in bulk single crystals and atomically thin films. While bulk PtSe2 and PtTe2 are type-II Dirac semimetals, monolayer (ML) PtSe2 film is a semiconductor with helical spin texture induced by local Rashba effect. However, the properties of atomically thin PtTe2 films and the evolution with film thickness remain unexplored. Recently, Shuyun Zhou’s group from Tsinghua University reported a systematic study on the electronic structure of high quality PtTe2 thin films with thickness from 2 ML to 6 ML grown by molecular beam epitaxy (MBE). This work provides direct experimental evidence for a crossover from 2-D metal (2ML film, distinguished from the semiconducting PtSe2 film) to 3-D Dirac semimetal in PtTe2 films with spin texture induced by local Rashba effect.
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Source: Phys.org