Pseudogap-Driven Sign Reversal of the Hall Effect

We present a calculation of the Hall coefficient in 2H -TaSe₂ and 2H-Cu_0.2NbS₂ based on their electronic structure extracted from angle-resolved photoemission spectra. The well-known semiclassical approach, based on the solution of the Boltzmann equation, yields the correct value for the normal-state Hall coefficient. Entering the charge density wave state results in the opening of the pseudogap and redistribution of the spectral weight. Accounting for this allows us to reproduce the temperature dependence of the Hall coefficient, including the prominent sign change, with no adjustable parameters.