Terahertz magnetotransport measurements in underdoped ${\text{Pr}}_{2-x}{\text{Ce}}_x{\text{CuO}}_4$ and comparison with angle-resolved photoemission

We present magnetotransport measurements performed on underdoped ${\text{Pr}}_{2-x}{\text{Ce}}_x{\text{CuO}}_4$ at THz frequencies as a function of temperature and doping. A rapidly decreasing Hall mass is observed as the doping is reduced consistent with the formation of small electron Fermi pockets. However, both dc and infrared magnetotransport data strongly deviate from the predictions of transport theory within the relaxation-time approximation based on angular-resolved photoemission data. Furthermore, the Hall mass remains negative with no signature of a change in Fermi-surface topology at or above the Néel temperature and the characteristic temperature at which the optical gap fully closes. In the paramagnetic state, this behavior of the Hall mass may be qualitatively understood as arising from current vertex corrections to the Hall conductivity due to magnetic fluctuations as observed in overdoped ${\text{Pr}}_{2-x}{\text{Ce}}_x{\text{CuO}}_4$ [G. S. Jenkins et al., arXiv:0901.1701 (unpublished)].

Figure 1

(Color online) (a) Real and imaginary parts of the Hall angle measured at 10.5 meV as a function of temperature. A negative value implies a dominant electronlike response. Grey depicts an uncertainty of one standard deviation. (b) Schematic of the FS model of the electron pocket centered at $\left(\pi ,0\right)$ as described in the text.

Figure 2

(Color online) (a) The Hall mass is extracted from Fig. 1a using Eq. (2) and normalized to the bare electron mass. Temperatures above 200 K are excluded due to noise introduced into $m_H$ from the exceedingly small Hall angle. The negative value of the Hall mass signifies a net electronlike response. The extremely small Hall masses associated with the 10% and 12% samples exemplify a large IR Hall response which cannot be obtained from ARPES data analyzed in terms of the RTA. The system fails to recover to a large holelike Fermi surface (positive $m_H$) well above the Néel temperature (marked by the lower temperature black arrows) (Ref. 13) as well as the characteristic temperature where the optical gap fully closes (marked by the higher temperature red arrows) (Ref. 3). (b) The low-temperature (28 K) Hall mass plotted versus doping.