Bandgap opening in few-layered monoclinic MoTe 2

Dong Hoon Keum, Suyeon Cho, Jung Ho Kim, Duk Hyun Choe, Ha Jun Sung, Min Kan, Haeyong Kang, Jae Yeol Hwang, Sung Wng Kim, Heejun Yang, K. J. Chang, Young Hee Lee

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Layered transition metal dichalcogenides (TMDs) have attracted renewed interest owing to their potential use as two-dimensional components in next-generation devices. Although group 6 TMDs, such as MX 2 with M = (Mo, W) and X = (S, Se, Te), can exist in several polymorphs, most studies have been conducted with the semiconducting hexagonal (2H) phase as other polymorphs often exhibit inhomogeneous formation. Here, we report a reversible structural phase transition between the hexagonal and stable monoclinic (distorted octahedral or 1T′) phases in bulk single-crystalline MoTe 2. Furthermore, an electronic phase transition from semimetallic to semiconducting is shown as 1T′-MoTe 2 crystals go from bulk to few-layered. Bulk 1T′-MoTe 2 crystals exhibit a maximum carrier mobility of 4,000 cm 2 V -1 s -1 and a giant magnetoresistance of 16,000% in a magnetic field of 14 T at 1.8 K. In the few-layered form, 1T′-MoTe 2 exhibits a bandgap opening of up to 60 meV, which our density functional theory calculations identify as arising from strong interband spin-orbit coupling. We further clarify that the Peierls distortion is a key mechanism to stabilize the monoclinic structure. This class of semiconducting MoTe 2 unlocks the possibility of topological quantum devices based on non-trivial Z 2 -band-topology quantum spin Hall insulators in monoclinic TMDs (ref.).

Original languageEnglish
Pages (from-to)482-486
Number of pages5
JournalNature Physics
Issue number6
StatePublished - 4 Jun 2015

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