Figure 1

Pressure-temperature ($P$-$T$) phase diagram of $\kappa$-(ET)${}_2$Cu[N(CN)${}_2$]$Z$ at zero magnetic field. The dashed line labeled $T_N$ indicates the paramagnetic-to-antiferromagnetic transition, the dash-dotted line labeled $T_c$ corresponds to the transition into bulk superconductivity, and the thick solid line labeled $T_{\mathrm{MI}}$ marks the first-order metal-to-insulator transition. D8-Br and H8-Br (position estimated according to Ref. 2) refer to the position of the deuterated and protonated single crystals of $\kappa$-(ET)${}_2$Cu[N(CN)${}_2$]Br, respectively. The vertical dotted line indicates the performed $T$ sweeps for “D8-Br” crystals, illustrating a crossing of the $S$-shaped line. Open symbols refer to literature data for the critical end point ($P_0$, $T_0$): $\diamond$ (Ref. 3), $▽$ (Ref. 4), $◯$ (Ref. 5), $△$ (Ref. 6), and $▴$ (Ref. 7). The position of the solid circle, corresponding to $T_{\mathrm{MI}}$ for the present crystal, implies that at this point in the phase diagram $T_{\mathrm{MI}}$ coincides with $T_N$ (cf. Ref. 8).Reuse & Permissions

Figure 2

Values of $\alpha \left(T\right)$ along the $b$ axis for single-crystal $\kappa$-(D8-ET)${}_2$Cu[N(CN)${}_2$]Br. Inset: magnification of the low-temperature ${\alpha }_b\left(T\right)$ data (left scale) together with results of the resistance normalized to the room-temperature value (right scale). $T_{\mathrm{MI}}$ refers to the MI transition temperature and $T_c$ denotes the critical temperature to percolative SC.Reuse & Permissions

Figure 3

Values of $\alpha \left(T\right)$ for single-crystal $\kappa$-(D8-ET)${}_2$Cu[N(CN)${}_2$]Br measured along the $b$ axis at low temperatures under selected fields, as indicated. Solid lines are a guide for the eyes. $T_{\mathrm{FI}}$ refers to the magnetic field induced transition temperature and $T_{\mathrm{MI}}$ to the metal-to-insulator transition temperature. Data taken at 0.5, 1, 2, 4, 6, and 10 T are shifted vertically for clarity.Reuse & Permissions

Figure 4

Schematic $B$-$T$ diagram for $\kappa$-D8-Br. Symbols refer to the peak anomaly in ${\alpha }_b\left(T\right)$. Diamonds: peak position of the anomaly in ${\alpha }_b$ associated with the metal-to-insulator transition, AFI $+$ Perc. SC refers to the antiferromagnetic insulating phase coexisting with percolative superconductivity, while SF $+$ Perc. SC indicates the spin-flopped phase coexisting with percolative superconductivity. Lines represent the various phase transitions discussed in the main text. PM and PI denote paramagnetic metal and paramagnetic insulator, respectively. The hatched region indicates the $T$ window in which a double-peak structure in ${\alpha }_b\left(T\right)$ is observed. The spin-reoriented phase refers to the region where ${\mathbf{M}}_A^{†}$ and ${\mathbf{M}}_B^{†}$ are antiparallel, giving rise to an interplane antiferromagnetic ordering as discussed in the main text (cf. Ref. 14).Reuse & Permissions