Studies of dynamic critical behavior in Bi2Sr2CaCu2O8+delta single crystals

Up to now, the value of the dynamic critical exponent z is still an open qu estion. We have studied this exponent in the intermediate (XY) critical reg ime in zero field for a set of high quality Bi2Sr2CaCu2O8+delta single crys tals both by previously obtained critical exponents of the de critical cond uctivity fluctuations [1] and in terms of Fisher-Fisher-Huse (FFH) dynamic scaling [2]. In this regime (i.e. the absence of Coulomb interactions), one would expect model-E dynamics (z = 1.5) to apply with the conserved charge -density conjugate to the phase fluctuations. However, we find the dynamic critical exponent to be z = 2, which is in agreement with the suggestion of FFH that due to the plasma fluctuation, fully relaxational dynamics, model A (z = 2), should be appropriate.