Metastability line in BSCCO phase diagram

Nonlinear charge transport in the low temperature vortex I:lass state of si ngle crystal Bi2Sr2CaCU2O8 superconductor has been investigated with fast c urrent pulses driven along the ab plane. Field cooled (FC) preparation show s a higher threshold current than zero field cooled (ZFC) one, but is found to be metastable and convertible to the ZFC response by a small field excu rsion. The metastability appears on the low temperature side of the peak in the temperature dependence of the ZFC threshold current. It is suggested t hat the onset of metastability signals a new thermodynamic ground state.