Effect of anion doping on Hall sign anomaly in the mixed-state of Tl2Ba2CuO6+delta thin films

The mixed-state Hall effect has been studied in Tl2Ba2CuO6 + delta thin fil ms with oxygen content tuned from underdoped to overdoped. Two sign reversa ls observed both in the underdoped and optimally doped samples disappear si multaneously when the sample is slightly overdoped. These results contradic t the prediction of the time-dependent Ginzberg-Landau and microscopic theo ries but confirm that both Hall sign reversals are determined by electronic band structure. Unlike the previous experiment, our results show that the Hall sign in the underdoped region may be either hole-like or electron-like in the superconducting state.