In a generic spin-polarized Fermi liquid, the masses of spin-up and spin-down electrons are expected to be different and to depend on the degree of polarization. This expectation is not confirmed by the experiments on two-dimensional heterostructures. We consider a model of an N-fold degenerate electron gas. It is shown that in the large-N limit, the mass is enhanced via a polaronic mechanism of emission/absorption of virtual plasmons. As plasmons are classical collective excitations, the resulting mass does not depend on N, and thus on polarization, to the leading order in 1/N. We evaluate the 1/N corrections and show that they are small even for N=2.
@article{arxiv.cond-mat/0505534,
title = {Spin-independent effective mass in a valley-degenerate electron system},
author = {Suhas Gangadharaiah and Dmitrii L. Maslov},
journal= {arXiv preprint arXiv:cond-mat/0505534},
year = {2011}
}