An indirect exciton (IX), also known as an interlayer exciton, is a bound pair of an electron and a hole confined in spatially separated layers. Due to their long lifetimes, IXs can cool below the temperature of quantum degeneracy. This provides an opportunity to experimentally study cold composite bosons. This article overviews our studies of cold IXs, presenting spontaneous coherence and Bose–Einstein condensation of IXs and phenomena observed in the IX condensate, including the spatially ordered exciton state, commensurability effect of exciton density wave, spin textures, Pancharatnam–Berry phase, long-range coherent spin transport, and interference dislocations.

间接激子（IX），也称为层间激子，是电子和空穴的结合对，它们限制在空间分隔的层中。由于它们的使用寿命长，IX可以冷却到低于量子简并温度。这为实验研究冷复合玻色子提供了机会。本文概述了我们对冷IX的研究，展示了IX的自发相干性和Bose-Einstein凝聚以及在IX冷凝物中观察到的现象，包括空间有序激子态，激子密度波的可比性效应，自旋织构，Pancharatnam-Berry相，长距离相干自旋输运和干涉位错。