Conductivity of a spin-polarized two-dimensional electron liquid in the ballistic regime

In the ballistic regime, the metallic temperature dependence of the conductivity in a two-dimensional electron system in silicon is found to change nonmonotonically with the degree of spin polarization. In particular, it fades away just before the onset of complete spin polarization but reappears again in the fully spin-polarized state, being, however, suppressed relative to the zero-field case. Analysis of the degree of the suppression allows one to distinguish between the screening and the interaction-based theories.

Figure 1

Conductivity, mobility, and elastic scattering time vs electron density at a temperature of $0.1\mathrm{K}$ for spin-unpolarized (triangles) and fully spin-polarized (circles) states in two slightly different samples A at $B=0$ and $9.5\mathrm{T}$ (a) and B at $B=0$ and $14\mathrm{T}$ (b).

Figure 2

Magnetoresistance at temperatures 0.5 (solid line), 0.8 (dashed line), and $1.2\mathrm{K}$ (dotted line) on sample B. The inset shows a detailed view of the magnetoresistance just before the onset of complete spin polarization.

Figure 3

Change of the resistance ratio $\rho \left(B_{\mathrm{sat}}\right)∕\rho \left(0\right)$ with electron density in sample B. The inset shows the normalized magnetoresistance, measured at the highest temperature used in this experiment, at electron densities $1.46\times {10}^{11}{\mathrm{cm}}^{-2}$ (dotted line) and $2.13\times {10}^{11}{\mathrm{cm}}^{-2}$ (solid line). The field of resistance saturation is marked by arrows.

Figure 4

The slope ratio as a function of electron density for samples A (circles) and B (squares). The inset shows the temperature dependence of the conductivity in both the fully spin-polarized state for $n_s=1.85\times {10}^{11}{\mathrm{cm}}^{-2}$ and the unpolarized state for $n_s=1.7\times {10}^{11}{\mathrm{cm}}^{-2}$ on sample A. The dashed lines are fits of the linear interval of the dependence.