Unusual Hall Effect in Superconducting MgB${}_2$ Films: Analogy to High-T${}_c$ Cuprates

Abstract

We have investigated the temperature and magnetic field dependence of the Hall coefficient of two well-characterized superconducting MgB${}_2$ films (T${}_{c0}$=38.0 K) in both the normal and superconducting states. Our results show that the normal-state Hall coefficient R${}_H$ is positive and increases with decreasing temperature, independent of the applied magnetic field. Below T${}_c$(H), R${}_H$ decreases rapidly with temperature and changes sign before it reaches zero. The position and magnitude at which R${}_H$ shows a minimum depends on the applied field. Quantitative analysis of our data indicates that the Hall response of MgB${}_2$ behaves very similarly to that of high-T${}_c$ cuprates: R${}_H$ $\propto$ T and cot${\theta }_H$ $\propto$ T${}^2$ in the normal state, and a sign reversal of R${}_H$ in the mixed state. This suggests that the B-B layers in MgB${}_2$, like the Cu-O planes in high-T${}_c$ cuprates, play an important role in the electrical transport properties.