10:30 〜 11:00
▲ [19a-S221-3] Electronic and optical properties of monoclinic MoTe2
キーワード：Transition metal dichalcogenides,phase transition
Transition metal dichalcogenides (TMDs), together with metallic graphene and highly insulating hexagonal boron nitride, have recently attracted renewed interests as an important two-dimensional component of next-generation devices. In particular, polymorph engineering in group 6 TMDs, such as MX2 with M=(Mo, W) and X=(S, Se, Te), has been an intriguing theme in science for more than 50 years; most researches have been conducted with semiconducting hexagonal (2H) phase, however other polymorphs have not been explored due to their inhomogeneous formation in limited areas.
In this talk, I will discuss on structural phase transition between hexagonal and stable monoclinic (distorted octahedral or 1T’) phase in bulk single-crystalline MoTe2, and an electronic phase transition between semi-metallic (bulk) and semiconducting (few-layered) 1T’-MoTe2. The newly discovered 1T’-MoTe2 exhibits a maximum carrier mobility of 4,000 cm2V-1s-1 and a giant magnetoresistance of 16,000% in a magnetic field of 14 Tesla at 1.8 Kelvin in the bulk form, and the few-layered 1T’-MoTe2 reveals a bandgap of up to 60 meV in monoclinic TMDs. Our density functional theory calculations identify strong interband spin-orbit coupling (SOC) as the origin of bandgap opening in the few-layered monoclinic MoTe2. It will be shown that the Peierls distortion is a key mechanism to stabilize the monoclinic structure. This new class of semiconducting MoTe2 unlocks the possibility of topological quantum devices based on nontrivial Z2-band-topology quantum spin Hall insulators in monoclinic TMDs and low interface resistance 2D semiconductor devices.
In this talk, I will discuss on structural phase transition between hexagonal and stable monoclinic (distorted octahedral or 1T’) phase in bulk single-crystalline MoTe2, and an electronic phase transition between semi-metallic (bulk) and semiconducting (few-layered) 1T’-MoTe2. The newly discovered 1T’-MoTe2 exhibits a maximum carrier mobility of 4,000 cm2V-1s-1 and a giant magnetoresistance of 16,000% in a magnetic field of 14 Tesla at 1.8 Kelvin in the bulk form, and the few-layered 1T’-MoTe2 reveals a bandgap of up to 60 meV in monoclinic TMDs. Our density functional theory calculations identify strong interband spin-orbit coupling (SOC) as the origin of bandgap opening in the few-layered monoclinic MoTe2. It will be shown that the Peierls distortion is a key mechanism to stabilize the monoclinic structure. This new class of semiconducting MoTe2 unlocks the possibility of topological quantum devices based on nontrivial Z2-band-topology quantum spin Hall insulators in monoclinic TMDs and low interface resistance 2D semiconductor devices.