We study the behavior of the Hall coefficient, $R_H$, in a system exhibiting $d_{ { x^2}-{ y^2}}$ density-wave (DDW) order in a regime in which the carrier concentration, $x$, is tuned to approach a quantum critical point at which the order is destroyed. At the mean-field level, we find that $n_{ \rm Hall}=1/R_H$ evinces a sharp signature of the transition. There is a kink in $n_{ \rm Hall}$ at the critical value of the carrier concentration, $x_c$; as the critical point is approached from the ordered side, the slope of $n_{ \rm Hall}$ diverges. Hall transport experiments in the cuprates, at high magnetic fields sufficient to destroy superconductivity, should reveal this effect.
Categories: cond-mat.supr-con cond-mat.str-el