Hall anomaly and vortex charge in Bi2Sr2CaCu2Ox (Bi2212)

The sign reversal of the Hall coefficient in the cuprates superconductors, the "Hall anomaly", is still an open question in the field of high-Tc superconductors.

The Hall sign change was attributed to different effects, including various vortex dynamics, competing phases to superconductivity, and vortex charge among others.

We present a systematic study of the Hall conductance in Bi2Sr2CaCu2Ox (Bi2212) thin films over a large

range of doping. We find that in a large part of the phase diagram the Hall coefficient changes sign as a function

of temperature in the flux-flow regime. By comparing data from many samples, we show that the sign reversal

is tied to the superconducting transition and is not a result of a competing order. The measurement in the flux-flow regime allows us to access the superconductivity-suppressed state which is present in the vortex cores, otherwise accessible only by the use of very high magnetic fields. We then compare our data

to the predictions of the Bardeen-Stephan model and show that in all samples there is an additional negative

contribution to the Hall conductivity. We extract from the negative excess Hall a vortex-charge that is found to

be strongly doping dependent.