Charge density wave order in 1D mirror twin boundaries of single-layer MoSe2

By S. Barja, Sebastian Wickenburg, Zhen-Fei Liu, Yi Zhang, H. Ryu, M. M. Ugeda, Z. Hussain, Zhi-xun Shen, S. Mo, E. Wong and 6 more. Nature Physics, 2016

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A scanning tunnelling microscopy study demonstrates that one-dimensional charge density waves can form at twin boundaries in a monolayer transition metal dichalcogenide. We provide direct evidence for the existence of isolated, one-dimensional charge density waves at mirror twin boundaries (MTBs) of single-layer semiconducting MoSe2. Such MTBs have been previously observed by transmission electron microscopy and have been predicted to be metallic in MoSe2 and MoS21,2,3,4,5,6,7. Our low-temperature scanning tunnelling microscopy/spectroscopy measurements revealed a substantial bandgap of 100 meV opening at the Fermi energy in the otherwise metallic one-dimensional structures. We found a periodic modulation in the density of states along the MTB, with a wavelength of approximately three lattice constants. In addition to mapping the energy-dependent density of states, we determined the atomic structure and bonding of the MTB through simultaneous high-resolution non-contact atomic force microscopy. Density functional theory calculations based on the observed structure reproduced both the gap opening and the spatially resolved density of states.

Subfields: Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/6138006b6cfcc3dc9a013800c45305ccb188b6a8