title: Glass-glass transition during aging of a colloidal clay.
abstract: Colloidal suspensions are characterized by a variety of microscopic interactions, which generate unconventional phase diagrams encompassing fluid, gel and glassy states and offer the possibility to study new phase and/or state transitions. Among these, glass-glass transitions are rare to be found, especially at ambient conditions. Here, through a combination of dilution experiments, X-ray photon correlation spectroscopy, small angle X-ray scattering, rheological measurements and Monte Carlo simulations, we provide evidence of a spontaneous glass-glass transition in a colloidal clay. Two different glassy states are distinguished with evolving waiting time: a first one, dominated by long-range screened Coulombic repulsion (Wigner glass) and a second one, stabilized by orientational attractions (Disconnected House of Cards glass), occurring after a much longer time. These findings may have implications for heterogeneously charged systems out-of-equilibrium and for applications where a fine control of the local order and/or long term stability of the amorphous materials are required.
authors.affiliation: 1] IPCF-CNR, UOS Roma, P.le Aldo Moro 2, I-00185 Roma, Italy [2] Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 2, I-00185 Roma, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Angelini
authors.affiliation: 1] Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 2, I-00185 Roma, Italy [2] ISC-CNR, UOS Sapienza, P.le Aldo Moro 2, I-00185 Roma, Italy.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Zaccarelli
authors.affiliation: Center for Life NanoScience, IIT@Sapienza, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Roma, Italy.
authors.forename: Flavio Augusto
authors.initials: FA
authors.lastname: de Melo Marques
authors.affiliation: ESRF-The European Synchrotron, CS40220, 38043 Grenoble Cedex 9, France.
authors.forename: Michael
authors.initials: M
authors.lastname: Sztucki
authors.affiliation: Brookhaven National Laboratory, NSLS-II, Upton, New York 11973, USA.
authors.forename: Andrei
authors.initials: A
authors.lastname: Fluerasu
authors.affiliation: 1] Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 2, I-00185 Roma, Italy [2] Center for Life NanoScience, IIT@Sapienza, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Roma, Italy.
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Ruocco
authors.affiliation: 1] IPCF-CNR, UOS Roma, P.le Aldo Moro 2, I-00185 Roma, Italy [2] Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 2, I-00185 Roma, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Ruzicka