Domain Coarsening and Aging in Dislocation Glasses

Dislocation systems were analyzed numerically with 1 and 3 glide axes, at T=0 and T$>$0, with and without climb. [1] Dislocation free domains formed even without shear, defined by dislocation rich domain walls. The domain formation was most pronounced in the presence of climb, somewhat counter-intuitively. The stability of domains was analyzed. The microscopic processes suppressing the climb-induced decay of domain walls were identified. The dislocation dynamics at low temperatures was markedly glassy. \underline {Aging:} Dislocations with glide only support minimal domain formation. The autocorrelation function showed aging, scaling with the waiting time as: C(t,t$_{w})$ = C$_{eq}$(t) C(t/t$_{w}^{\mu })$ and C$_{eq}$(t) $\sim $ t$^{-\beta }$, with $\mu $=0.65 and $\beta $=0.54. \underline {Freezing:} The effective diffusion constant decayed to zero as: D(t)$_{eff} \quad \sim $ t$^{-\gamma }$ , with $\gamma $=0.8. \underline {Coarsening:} Dislocations with glide and climb exhibited profound domain formation, the domains coarsening as L(t): L(t) $\sim $ t$^{1/z}$, with 1/z=0.17. The formation of domains without shear has been recently observed in GaAs by Rudolph and in dusty plasmas by Quinn and Joree. The domain coarsening was quantitatively captured in di-block copolymers [2], with 1/z=0.19, in good agreement with our results. \newline \newline [1] B. Bako, G. Groma, G. Gyorgyi and G.T. Zimanyi, Phys. Rev. Lett. \textbf{98}, 075701 (2007). \newline [2] P. Chaikin's talk, same session.