Anomalous Suppression of the Vortex Hall Current in UnderdopedYBa₂Cu₃O_x

The transport properties of underdoped YBa₂Cu₃O_x (YBCO) crystals with x = 6.95, 6.80, 6.66 were measured and the effect of pseudogap on the Hall conductivity was studied. In the normal state, the Hall angle remains unperturbed at the crossover temperature of resistivity for the underdoped samples. An anomalous suppression of the vortex Hall current was observed near T_c and the contribution of the vortices to the Hall current is absent above 4K in 6K YBCO (x = 6.66).