Evidence of a glass transition in a 10-state non-mean-field Potts glass

Potts glasses are prototype models that have been used to understand the structural glass transition. However, in finite space dimensions a glass transition remains to be detected in the 10-state Potts glass. Using a one-dimensional model with long-range power-law interactions we present evidence that a glass transition below the upper critical dimension can exist for short-range systems at low enough temperatures. Gaining insights into the structural glass transition for short-range systems using spin models is thus potentially possible, yet difficult.Comment: 4 pages, 1 table, 2 figure

Qualitative change in structural dynamics of some glass-forming systems

Analysis of temperature dependence of structural relaxation time in supercooled liquids revealed a qualitatively distinct feature - a sharp, cusp-like maxumum in the second derivative of its logarithm. It suggests that the super-Arrhenius behavior of the structural relaxation time in glass-forming liquids eventually crosses over to the Arrhenius behavior below the temperature of maximum, and there is no divergence of the relaxation time at non-zero temperature. The position of the maximum can be both above or below glass transition temperature, depending on the sensitivity of the structural relaxation time to changes in density. These results might turn the discussion of the glass transition to the new avenue - the origin of the limiting activation energy for structural relaxation at low temperatures

Equations of structural relaxation

In the mode coupling theory of the liquid to glass transition the long time structural relaxation follows from equations solely determined by equilibrium structural parameters. The present extension of these structural relaxation equations to arbitrarily short times on the one hand allows calculations unaffected by model assumptions about the microscopic dynamics and on the other hand supplies new starting points for analytical studies. As a first application, power-law like structural relaxation at a glass-transition singularity is explicitly proven for a special schematic MCT model.Comment: 11 pages, 3 figures; talk given at the Seventh international Workshop on disordered Systems, Molveno, Italy, March 199

Random Pinning Glass Model

Glass transition where viscosity of liquids increases dramatically upon decrease of temperature without any major change in structural properties, remains one of the most challenging problems in condensed matter physics (Cavagna, 2009; Berthier and Biroli, 2011) in spite of tremendous research efforts in last decades. On the other hand disordered freezing of spins in a magnetic materials with decreasing temperature, the so-called spin glass transition, is relatively better understood (Mezard, Parisi and Virasoro, 1987; Castellani and Cavagna, 2005). Previously found similarity between some spin glass models with the structural glasses (Kirkpatrick and Thirumalai, 1987; Kirkpatrick and Wolynes, 1987; Kirkpatrick and Wolynes, 1987; Franz and Parisi, 1999; Moore and Drossel, 2002) inspired development of theories of structural glasses (Kirkpatrick, Thirumalai and Wolynes, 1989; Barrat, Franz and Parisi, 1997; M\'ezard and Parisi, 1999; Lubchenko and Wolynes, 2007; Biroli and Bouchaud, 2012) based on the scenario of spin glass transition. This scenario though looks very appealing is still far from being well established. One of the main differences between standard spin systems to molecular systems is the absence of quenched disorder and the presence of translational invariance: it often assumed that this difference is not relevant, but this conjecture is still far from being established. The quantities, which are well defined and characterized for spin models, are not easily calculable for molecular glasses due to the lack of quenched disorder which breaks the translational invariance in the system and the characterization of the similarity between the spin and the structural glass transition remained an elusive subject still now. In this study we introduced a model structural glass with built in quenched disorder which alleviates this main difference between the spin and molecular glasses thereby helping us to compare these two systems: the possibility of producing a good thermalization at rather low temperatures is one of the advantages of this model.Comment: Submitted to PNAS with 7 pages 5 figures and Supplementary Material

Structural Relaxation and Mode Coupling in a Simple Liquid: Depolarized Light Scattering in Benzene

We have measured depolarized light scattering in liquid benzene over the whole accessible temperature range and over four decades in frequency. Between 40 and 180 GHz we find a susceptibility peak due to structural relaxation. This peak shows stretching and time-temperature scaling as known from $\alpha$ relaxation in glass-forming materials. A simple mode-coupling model provides consistent fits of the entire data set. We conclude that structural relaxation in simple liquids and $\alpha$ relaxation in glass-forming materials are physically the same. A deeper understanding of simple liquids is reached by applying concepts that were originally developed in the context of glass-transition research.Comment: submitted to New J. Phy

Relaxation dynamics of Fe55Cr10Mo14C15B6 metallic glass explored by mechanical spectroscopy and calorimetry measurements

In this work, the mechanical relaxation dynamics of Fe55Cr10Mo14C15B6 metallic glass is explored by mechanical spectroscopy. The temperature-dependent loss modulus E″(T) shows the features of β relaxation well below glass transition temperature Tg. This β relaxation can be well described in the framework of anelastic theory by a thermal activated process with activation energy of 165 kJ mol−1. Structural relaxation, also known as physical aging, has a large effect on the glass properties. The activation energy spectrum of structural relaxation is characterized by differential scanning calorimetry measuring the heat flow difference between as-quenched and relaxed states. The obtained energy spectrum is well described by a lognormal distribution with maximum probability activation energy of 176 kJ mol−1. The obtained activation energy of structural relaxation is similar to that of β relaxation observed from mechanical spectroscopy. Both values are also close to the Johari–Goldstein β relaxation estimated by the empirical rule Eβ = 26RTg.Peer ReviewedPostprint (author's final draft