In two-dimensional crystals, electrons and holes, quasiparticles corresponding to the absence of an electron and carrying positive charge, attract each other, forming bound pairs called excitons. When cooled strongly, as thermal fluctuations die down, the motions of many excitons can synchronize, like a coordinated dance. This gives rise to a Bose-Einstein condensate — a macroscopic quantum wave in which all particles occupy a single state. The long-range electric attraction acting between the components of the pairs twists this wave into a vortex containing two Weyl points. At these points, the energy flow behaves as if it flows into and out of special regions of space.

Such a vortex structure leads to the appearance of edge currents that flow without resistance: these are ideal conductors at the material's boundary. This property brings the system closer to hypothetical particles described by the Standard Model of particle physics. Experimental confirmation of these effects requires precise surface spectroscopy — a method that probes energy states. Success in this direction paves the way for creating ultra-sensitive sensors and quantum processors.