日時
2017年11月28日(火) 16:30–
場所
大阪大学サイバーメディアセンター 7F 会議室
題目
Attacking the Glass Problem by Getting Low in the Energy Landscape: Nano-Particle Resolved Studies and Large Deviations
発表者
Paddy Royall 氏 (ブリストル大)
要旨

Our understanding of the mechanism by which the viscosity of supercooled liquids increase by many decades is hampered by the difficulty in discriminating apparently incompatible theoretical approaches. The challenge lies in equilibrating samples at sufficient supercooling that experimental or numerical techniques can probe suitable quantities that enable the theories to be discriminated, or by directly testing the theories. Recently, considerable progress has been made in obtaining data which can help to discriminate such theories, in both molecular experiments and simulation [1]. Much of these new data tend to support theories which imagine a thermodynamic origin of the glass transition – in contrast to a predominately dynamic one. Of the thermodynamic theories, we begin by probing the predictions of the geometric frustration theory of the glass transition [2].

Nevertheless, plenty of compelling evidence in support of dynamic facilitation (which posits that the glass transition is driven by a dynamical phase transition) exists [3], which we have shown can be accessed in experiments [4]. Here we present new results, which use novel techniques to obtain very deeply supercooled configurations in an atomistic model glassformer. These naturally lend themselves to a determination of the dynamical phase transition of facilitation. Consistent with results on certain lattice models [5], we find that the dynamical phase transition has a lower temperature bound, which we interpret as a critical point. Now our deeply supercooled configurations also give access to the configurational entropy, from which we can locate the Kauzmann temperature. Remarkably, within the accuracy of our approach, this point where the thermodynamic theories suggest a phase transition lies at the same temperature as the lower critical point of the dynamical transition. We suggest that our findings may lead to a path to reconcile the competing thermodynamic and dynamic interpretations of the glass transition [6].

[1] Royall, C. P.; Turci, F.; Tatsumi, S.; Russo, J. & Robinson, J. “The race to the bottom: approaching the ideal glass?”, ArXiV, 1711.04739 (2017).
[2] Turci, F.; Tarjus, G. & Royall, C. P. “From Glass Formation to Icosahedral Ordering by Curving Three-Dimensional Space”, Phys. Rev. Lett., 118, 215501 (2017).
[3] Speck, T.; Malins, A. & Royall, C. P. “First-Order Phase Transition in a Model Glass Former: Coupling of Local Structure and Dynamics” Phys. Rev. Lett. 109, 195703 (2012).
[4] Pinchaipat, R.; Campo, M.; Turci, F.; Hallet, J.; Speck, T. & Royall, C. P. “Experimental Evidence for a Structural-Dynamical Transition in Trajectory Space” Phys. Rev. Lett., 119, 028004 (2017).
[5] Turner, R. M.; Jack, R. L. & Garrahan, J. P. Overlap and activity glass transitions in plaquette spin models with hierarchical dynamics Phys. Rev. E, 92, 022115 (2015).
[6] Turci, F.; Royall, C. P. & Speck, T. Non-Equilibrium Phase Transition in an Atomistic Glassformer: the Connection to Thermodynamics Phys. Rev. X, 7 031028 (2017).