We demonstrate experimentally and theoretically that two-dimensional (2D) heavy hole systems in single heterostructures exhibit a \emph{decrease} in spin-orbit interaction-induced spin splitting with an increase in perpendicular electric field. Using front and back gates, we measure the spin splitting as a function of applied electric field while keeping the density constant. Our results are in contrast to the more familiar case of 2D electrons where spin splitting increases with electric field.
@article{arxiv.cond-mat/0409372,
title = {Negative differential Rashba effect in two-dimensional hole systems},
author = {B. Habib and E. Tutuc and S. Melinte and M. Shayegan and D. Wasserman and S. A. Lyon and R. Winkler},
journal= {arXiv preprint arXiv:cond-mat/0409372},
year = {2009}
}