Low-temperature structure of indium quantum chains on silicon

The array of quasi-one-dimensional indium chains in the Si(111)-(4 X 1)-In surface reconstruction exhibits a phase transition to a low-temperature (8 X 2) phase. It has been suggested that this phase transition is related to a charge density wave (CDW) formation. The x-ray diffraction results presen ted here demonstrate that at 20 K the CDW has not yet condensed into a supe rstructure even though good transverse coupling was established. This indic ates that CDW formation cannot be the driving force for the phase transitio n. Furthermore we elucidate the subtle highly anisotropic interchain correl ations and reveal the detailed atomic structure of the low-temperature (8 X 2) phase.