Anomalous high-temperature Hall effect on the triangular lattice in Na_xCoO_2

TL;DR

This paper investigates the anomalous high-temperature Hall effect in Na_xCoO_2, revealing strong electronic correlations and unusual linear temperature dependence of the Hall coefficient on a triangular lattice.

Contribution

It provides experimental evidence of anomalous Hall behavior in Na_xCoO_2 and compares it with theoretical predictions, highlighting the role of strong correlations and lattice geometry.

Findings

Hall coefficient increases linearly with temperature up to 8 times the Drude value

No saturation observed in the high-temperature Hall effect

Strong correlation effects are evidenced by the behavior of R_H and thermopower Q

Abstract

The Hall coefficient R_H of Na_xCoO_2 (x = 0.68) behaves anomalously at high temperatures. From 200 to 500 K, R_H increases linearly with T to 8 times the expected Drude value, with no sign of saturation. Together with the thermopower Q, the behavior of R_H provides firm evidence for strong correlation. We discuss the effect of hopping on a triangular lattice and compare R_H with a recent prediction by Kumar and Shastry.