Spin Polarization Dependence of the Coulomb Drag at Large $r_{s}$

TL;DR

This study investigates how spin polarization affects the temperature dependence of Coulomb drag resistivity in dilute two-dimensional hole systems, revealing a strong dependence near the metal-insulator transition and independence at higher densities.

Contribution

It demonstrates the influence of spin polarization on Coulomb drag behavior near the metal-insulator transition, highlighting a transition from spin-dependent to spin-independent regimes.

Findings

Drag resistivity's temperature dependence weakens with spin polarization near the transition.

The exponent α saturates at half its zero-field value beyond a critical magnetic field.

At higher densities, the temperature dependence remains consistent regardless of spin polarization.

Abstract

We find that the temperature dependence of the drag resistivity ($\rho_{D}$) between two dilute two-dimensional hole systems exhibits an unusual dependence upon spin polarization. Near the apparent metal-insulator transition, the temperature dependence of the drag, given by $T^{\alpha}$, weakens with the application of a parallel magnetic field ($B_{||}$), with $\alpha$ saturating at half its zero field value for $B_{||} > B^{*}$, where $B^{*}$ is the polarization field. Furthermore, we find that $\alpha$ is roughly 2 at the parallel field induced metal-insulator transition, and that the temperature dependence of $\rho_{D}/T^{2}$ at different $B_{||}$ looks strikingly similar to that found in the single layer resistivity. In contrast, at higher densities, far from the zero field transition, the temperature dependence of the drag is roughly independent of spin polarization, with $\alpha$ remaining close to 2, as expected from a simple Fermi liquid picture.