The Hall effect in Zn-doped YBa₂Cu₃O_(7-δ) revisited: Hall angle and the pseudogap

The temperature dependence of the Hall coefficient is measured with a high accuracy in a series of Zn-doped YBCO_{6.78} crystals with the Zn concentration from 0% to 1.3%. We found that the cotangent of the Hall angle, cot(\theta_H), starts to deviate upward from the T^2 dependence below T_0 (which is roughly 130 K), regardless of the Zn concentration. We discuss that this deviation is caused by the pseudogap; the direction of the deviation and its insensitivity to the Zn doping suggest that the pseudogap affects cot(\theta_H) through a change in the effective mass, rather than through a change in the Hall scattering rate.