High-Pressure Electronic State of κ-(BEDT-TTF)2Cu[N(CN)2]Br Probed by Hall Effect

We studied the normal-state properties of an organic superconductor, κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Br, through the investigation of the Hall effect as functions of temperature and pressure. At low pressures, the Hall coefficient shows an apparent increase with lowering temperature and a following peak structure. In this pressure range, the Hall effect possibly correlates with the spin fluctuation. At high pressures, we observed a drastic decrease and sign change in the Hall coefficient. With the dissimilarity with the behavior of similar compounds such as κ-(BEDT-TTF) 2 Cu(NCS) 2 and κ-(BEDT-TTF) 2 Cu(N[CN] 2 )Cl, we concluded that this behavior originates from a superstructure below 200 K.