"Charge density wave order in 1D mirror twin boundaries of single-layer MoSe"
Sara Barja: Sebastian Wickenburg, Zhen-Fei Liu, Yi Zhang, Hyejin Ryu, Miguel M. Ugeda, Zahid Hussain, Zhi-Xun Shen, Sung-Kwan Mo, Ed Wong, Miquel B. Salmeron, Feng Wang, Michael F. Crommie, D. Frank Ogletree, Jeffrey B. Neaton & Alexander Weber-Bargioni; Nat Phys, 04/18/16.
Abstract:
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.