Figure 1
Illustration: Alan Stonebraker

Figure 1: In the one-dimensional world, an electron that carries both spin and charge cannot exist as a well-defined particle. It splits into two collective excitations, one carrying spin but not charge (the spinon), the other carrying charge but not spin (the holon). This is one of the basic properties of the Luttinger-liquid theory, the cornerstone for the description of one-dimensional materials. Of course, in a quasi-one-dimensional material where several chains are close to each other, spinons and holons must recombine before a real electron can hop from one chain to the next.