Hexagon versus trimer formation in in nanowires on Si(111): Energetics and quantum conductance

The structural and electronic properties of the quasi-one-dimensional In=Si111 surface system are calculated from first principles. It is found that the symmetry lowering of the In chains is energetically favorable, provided neighboring nanowires are correlated, giving rise to a doubling of the surface unit cell both along and perpendicular to the chain direction. The recently suggested formation of hexagons within the In nanowires [C. Gonza´lez, F. Flores, and J. Ortega, Phys. Rev. Lett. 96, 136101 (2006)]--in clear contrast to the trimer formation proposed earlier--drastically modifies the electron transport along the In chains, in agreement with experiment.