title: Two-dimensional melting under quenched disorder.
abstract: We study the influence of quenched disorder on the two-dimensional melting behavior of superparamagnetic colloidal particles, using both video microscopy and computer simulations of repulsive parallel dipoles. Quenched disorder is introduced by pinning a fraction of the particles to an underlying substrate. We confirm the occurrence of the Kosterlitz-Thouless-Halperin-Nelson-Young scenario and observe an intermediate hexatic phase. While the fluid-hexatic transition remains largely unaffected by disorder, the hexatic-solid transition shifts to lower temperatures with increasing disorder. This results in a significantly broadened stability range of the hexatic phase. In addition, we observe spatiotemporal critical(like) fluctuations, which are consistent with the continuous character of the phase transitions. Characteristics of first-order transitions are not observed.
authors.affiliation: Fachbereich für Physik, Universität Konstanz, D-78464 Konstanz, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Deutschländer
authors.forename: Tobias
authors.initials: T
authors.lastname: Horn
authors.forename: Hartmut
authors.initials: H
authors.lastname: Löwen
authors.forename: Georg
authors.initials: G
authors.lastname: Maret
authors.forename: Peter
authors.initials: P
authors.lastname: Keim