Electron–hole bilayers are semiconductor structures in which electrons and holes—positively charged electron vacancies—are separated into two distinct layers. These structures can host unusual phases of matter owing to the presence of both attraction between opposite charges and repulsion between like charges. However, most studies have focused only on the scenario in which the electron density is equal to the hole density. Now theoretical work by David Dai and Liang Fu at the Massachusetts Institute of Technology has explored the imbalanced case in which this electron–hole density ratio is 2:1 [1]. The researchers’ findings suggest that such an electron–hole bilayer has a remarkably rich phase diagram.
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