Metastability and microscopic avalanche dynamics in charge-density waves of chromium

We have measured the relaxation of charge-density waves in chromium from out-of-equilibrium states achieved through rapid thermal quenching. Although pinned density waves have been predicted to relax through stick-slip dynamics, in which long-lived metastable states are linked by abrupt rearrangements of the microscopic structure, these microscopic behaviors have not been observed. Using synchrotron x rays, we have measured metastability of the order parameter and microscopic pinning phenomena including an avalanche of the charge-density wave phase. Molecular dynamical simulations based on the Fukuyama-Lee-Rice model show that these behaviors may be attributed to nucleation, pinning, and propagation of phase solitons.