Figure 1

(a) Zero-field MIT with a critical density $p_c\sim 0.8\times {10}^{10}/{\mathrm{cm}}^2$ in a 10 nm wide GaAs QW (sample 5B); $\rho (T)$ at $p=1.33$, 1.14, 0.94, 0.86, 0.82, 0.78, 0.75, 0.63, 0.55 are shown. (b) Magnetoresistivity of sample 5B with $p=0.86$ at $T=50\mathrm{mK}$, 65 mK, 80 mK, 0.1 K, 0.15 K, and 0.2 K. The reentrant insulating phase (RIP) resides between the $\nu =1$ and $\nu =2$ QH states. (c) Arrhenius plot of the resistance at the peak of the RIP from sample 11C ($p_c\sim 0.95\times {10}^{10}/{\mathrm{cm}}^2$) at densities of 0.9, 0.96, 1.03, 1.09, 1.15, and 1.21.( d) Fitted thermal activation gap ${\Delta }_{\mathrm{RIP}}$ vs hole densities in samples 5B and 11C.Reuse & Permissions

Figure 2

(a) Capacitance (symbol) and resistance (line) vs perpendicular magnetic field for QW 11D at 70 mK at $p=0.86$, 0.95, 1.02, 1.12, 1.25, 1.42, and 1.73. The $\nu =1$ QH state gradually weakens as the density decreases, and eventually disappears, followed by the emergence of the new RIP. The dashed line is the estimated value of geometric capacitance $C_0$.(b) Longitudinal resistance map of QW 11C in $p$-$B$ plane at 70 mK. As the color varies from red (in the $\nu =1\mathrm{QH}$) to violet (in the RIP or HFIP), the resistance increases from $\le 300\Omega$ to $\ge 300\mathrm{k}\Omega$ in a log scale. The area with resistance larger than $300\mathrm{k}\Omega$ is filled with violet. (c) Capacitance of QW 11D in $p$-$B$ plane at 70 mK. The capacitance drops from 2.7 to $\le 2.2\mathrm{nF}$ as the color changes from red (in the area between the $\nu =1\mathrm{QH}$ and the RIP or HFIP) to violet (in the $\nu =1\mathrm{QH}$ and RIP or HFIP).Reuse & Permissions

Figure 3

(a),(b),(c) Contour map of the longitudinal resistivity of a 10 nm wide $p$-type GaAs QW (sample QW 5B) in the $p$-$B$ plane at $T=150$, 80, and 50 mK. (d) Schematic phase diagram converted from Fig. 14 of Ref. 26b, in which the Wigner solid phase is predicted to exist between the 2D hole liquid at $B=0$ and the QH liquids at $\nu =1$ and $1/3$.Reuse & Permissions