"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.

Additional Authors: 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

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 MoS2123456,7. Our low-temperature scanning tunnelling microscopy/spectroscopy measurements revealed a substantial bandgap of 100meV 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.