Spin Polarization Transition in the Symmetric Electron-Electron and Electron-Hole Bilayers

Abstract

We explore the feasibility of the existence of a spin-polarization transition in the symmetric electron-electron and electron-hole bilayers. We accomplish this task by drawing a comparison between the ground-state energies of the unpolarized and fully polarized phases of the bilayer system. The ground-state energy calculation is performed by using the q-STLS (quantum Singwi, Tosi, Land, and Sjolander) theory. In addition, the numerical results are studied for the static density susceptibility and pair-correlation function over a wide range of layer parameters viz. particle density rsl, and layer spacing d. Interestingly enough, a spin-polarization transition is found to take place in both the electron-electron and electron-hole bilayers from the unpolarized to the polarized liquid well before the unpolarized liquid could actually make transition to the Wigner crystal (WC) state. The polarized electron-electron and electron-hole bilayers too support the charge density wave (CDW) and WC instabilities, but the crossover density is now lowered in comparison with their respective unpolarized counterparts.