Magnetic-Field-Induced Mott Transition in a Quasi-Two-Dimensional Organic Conductor

We investigated the effect of magnetic field on the highly correlated metal near the Mott transition in the quasi-two-dimensional layered organic conductor, $\kappa \mathrm{\text{−}}(\mathrm{B}\mathrm{E}\mathrm{D}\mathrm{T}\mathrm{\text{−}}\mathrm{T}\mathrm{T}\mathrm{F}{)}_2\mathrm{C}\mathrm{u}[\mathrm{N}(\mathrm{C}\mathrm{N}{)}_2]\mathrm{C}\mathrm{l}$, by the resistance measurements under control of temperature, pressure, and magnetic field. It was demonstrated that the marginal metallic phase near the Mott transition is susceptible to the field-induced localization transition of the first order, as was predicted theoretically. The thermodynamic consideration of the present results gives a conceptual pressure-field phase diagram of the Mott transition at low temperatures.

Figure 1

Pressure-temperature phase diagrams of $\kappa$-Cl under a zero field (a) taken from Ref. 9 and under a field of 11 T normal to the conducting layer (b). Closed and open circles represent points giving the first-order Mott transition and crossover, respectively. The AF transition lines (dotted line) and the AFI-SC boundary (dashed line) are taken after Lefebvre et al. [6].

Figure 2

Resistance curves under ascending (black) and descending (gray) fields normal to the conducting layer with temperature and pressure kept constant.

Figure 3

Magnetic-field dependence of resistance under various pressures at 7.1 K. The field is applied normal to the conducting layer. The black and gray points are for ascending and descending fields, respectively.

Figure 4

Conceptual pressure-field phase diagram at $T\sim 7\mathrm{K}$, which is well below $T_{\mathrm{C}}\sim 13\mathrm{K}$. The solid line represents the first-order transition.