The longitudinal resistivity ρxx of two-dimensional electron gases formed in wells with two subbands displays ringlike structures when plotted in a density--magnetic-field diagram, due to the crossings of spin-split Landau levels (LLs) from distinct subbands. Using spin density functional theory and linear response, we investigate the shape and spin polarization of these structures as a function of temperature and magnetic-field tilt angle. We find that (i) some of the rings "break" at sufficiently low temperatures due to a quantum Hall ferromagnetic phase transition, thus exhibiting a high degree of spin polarization (∼50%) within, consistent with the NMR data of Zhang \textit{et al.} [Phys. Rev. Lett. {\bf 98}, 246802 (2007)], and (ii) for increasing tilting angles the interplay between the anticrossings due to inter-LL couplings and the exchange-correlation (XC) effects leads to a collapse of the rings at some critical angle θc, in agreement with the data of Guo \textit{et al.} [Phys. Rev. B {\bf 78}, 233305 (2008)].
@article{arxiv.0909.2175,
title = {Many-body effects on the $\rho_{xx}$ ringlike structures in two-subband wells},
author = {Gerson J. Ferreira and Henrique J. P. Freire and J. Carlos Egues},
journal= {arXiv preprint arXiv:0909.2175},
year = {2010}
}