Unusual Hall Effect in Superconducting MgB₂ Films: Analogy to High-Tc Cuprates

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We have investigated the temperature and magnetic field dependence of the Hall coefficient of two well-characterized superconducting MgB₂ films (Tc₀=38.0 K) in both the normal and superconducting states. Our results show that the normal-state Hall coefficient Rₕ is positive and increases with decreasing temperature, independent of the applied magnetic field. Below Tc(H), Rₕ decreases rapidly with temperature and changes sign before it reaches zero. The position and magnitude at which Rₕ shows a minimum depends on the applied field. Quantitative analysis of our data indicates that the Hall response of MgB₂ behaves very similarly to that of high-Tc cuprates: Rₕ ∝ T and cotθₕ ∝ T² in the normal state, and a sign reversal of Rₕ in the mixed state. This suggests that the B-B layers in MgB₂, like the Cu-O planes in high-Tc cuprates, play an important role in the electrical transport properties.