Leonard J R, Hu Lunhui, High A A, Hammack A T, Wu Congjun, Butov L V, Campman K L, Gossard A C
Department of Physics, University of California at San Diego, La Jolla, CA, USA.
Materials Department, University of California at Santa Barbara, Santa Barbara, CA, USA.
Nat Commun. 2021 Feb 19;12(1):1175. doi: 10.1038/s41467-021-21353-7.
Interference patterns provide direct measurement of coherent propagation of matter waves in quantum systems. Superfluidity in Bose-Einstein condensates of excitons can enable long-range ballistic exciton propagation and can lead to emerging long-scale interference patterns. Indirect excitons (IXs) are formed by electrons and holes in separated layers. The theory predicts that the reduced IX recombination enables IX superfluid propagation over macroscopic distances. Here, we present dislocation-like phase singularities in interference patterns produced by condensate of IXs. We analyze how exciton vortices and skyrmions should appear in the interference experiments and show that the observed interference dislocations are not associated with these phase defects. We show that the observed interference dislocations originate from the moiré effect in combined interference patterns of propagating condensate matter waves. The interference dislocations are formed by the IX matter waves ballistically propagating over macroscopic distances. The long-range ballistic IX propagation is the evidence for IX condensate superfluidity.
干涉图样为量子系统中物质波的相干传播提供了直接测量方法。激子的玻色 - 爱因斯坦凝聚体中的超流性能够实现长程弹道式激子传播，并能导致出现长尺度干涉图样。间接激子（IXs）由分离层中的电子和空穴形成。理论预测，IX复合的减少能使IX在宏观距离上实现超流传播。在此，我们展示了由IX凝聚体产生的干涉图样中类似位错的相位奇点。我们分析了激子涡旋和斯格明子在干涉实验中应如何出现，并表明观察到的干涉位错与这些相位缺陷无关。我们表明，观察到的干涉位错源于传播的凝聚体物质波的组合干涉图样中的莫尔效应。干涉位错由IX物质波在宏观距离上的弹道式传播形成。长程弹道式IX传播是IX凝聚体超流性的证据。
