Slow relaxation of low temperature vortex phases in Bi_{2}Sr_{2}CaCu_{2}O_{8}

Nonlinear transport in the low temperature vortex glass state of single crystal Bi_{2}Sr_{2}CaCu_{2}O_{8} has been investigated over long times (up to two weeks) with fast current pulses driven along the ab plane. It is found that at low temperature and high magnetic field both zero field cooled (ZFC) and field cooled (FC) samples relax towards the same equilibrium state, which is much closer to the original ZFC state than to the FC state. The implication of this FC metastability for the vortex phase diagram is discussed in the context of previous measurements.
latex ageg.tex, 5 files, 4 figures, 5 pages [SPEC-S01/041], submitted to Phys. Rev. Lett. Text changes