Steady-state, effective-temperature dynamics in a glassy material

We present a shear-transformation-zone (STZ)-based analysis of numerical simulations by Haxton and Liu [Phys. Rev. Lett. 99, 195701 (2007)]. The extensive Haxton and Liu (HL) data sharply test the basic assumptions of the STZ theory, especially the central role played by the effective disorder temperature as a dynamical state variable. We find that the theory survives these tests, and that the HL data provide important and interesting constraints on some of its specific ingredients. Our most surprising conclusion is that, when driven at various constant shear rates in the low-temperature glassy state, the HL system exhibits a classic glass transition, including super-Arrhenius behavior, as a function of the effective temperature.