Nonlocal conductivity inBi2Sr2CaCu2O8+δcrystals

Using an eight-terminal geometry, we have measured voltages in ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_{8+\mathrm{\delta }}$ single crystals with current injected both parallel and perpendicular to the crystallographic c axis and with magnetic fields H⩽3 kOe, H‖c axis. In a range of fields and temperatures for which the conductivity is Ohmic, our results disagree with a model that assumes classical electrodynamics. We believe that interlayer vortex coupling is responsible for nonlocal conductivity in this regime.