  Starting from a Su-Schrieffer-Heeger-like model inferred from
first-principles simulations, we show that the metal-insulator transition in
In/Si(111) is a first-order grand canonical Peierls transition in which the
substrate acts as an electron reservoir for the wires. This model explains
naturally the existence of a metastable metallic phase over a wide temperature
range below the critical temperature and the sensitivity of the transition to
doping. Raman scattering experiments corroborate the softening of the two
Peierls deformation modes close to the transition.
