title: Specific heat in two-dimensional melting.
abstract: We report the specific heat cN around the melting transition(s) of micrometer-sized superparamagnetic particles confined in two dimensions, calculated from fluctuations of positions and internal energy, and corresponding Monte Carlo simulations. Since colloidal systems provide single particle resolution, they offer the unique possibility to compare the experimental temperatures of the peak position of cN(T) and symmetry breaking, respectively. While order parameter correlation functions confirm the Kosterlitz-Thouless-Halperin-Nelson-Young melting scenario where translational and orientational order symmetries are broken at different temperatures with an intermediate so called hexatic phase, we observe a single peak of the specific heat within the hexatic phase, with excellent agreement between experiment and simulation. Thus, the peak is not associated with broken symmetries but can be explained with the total defect density, which correlates with the maximum increase of isolated dislocations. The absence of a latent heat strongly supports the continuous character of both transitions.
authors.affiliation: Physics Department, University of Konstanz, 78464 Konstanz, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Deutschländer
authors.affiliation: Department of Applied Physics, University of Almeria, 04120 Almeria, Spain.
authors.forename: Antonio M
authors.initials: AM
authors.lastname: Puertas
authors.affiliation: Physics Department, University of Konstanz, 78464 Konstanz, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Maret
authors.affiliation: Physics Department, University of Konstanz, 78464 Konstanz, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Keim