Tusi Chye, or “Dan” to his friends, shared this year’s Nobel Prize in Physics for his pioneering experiments on the “fractional quantum Hall effect”. This effect is observed when the electrons responsible for electrical conduction, in a material cooled down and placed inside a magnet, behave as an incompressible “quantum fluid”. Tsui’s discovery came as a surprise, because theory had not predicted it.

The “quantum” in the name for such electrons sounds complicated but will be explained later. “Fluid” is the term used to describe matter that easily changes shape, so includes both gas and liquid. A gas, like air, also readily changes volume but liquids, like seawater, do not. So physicists are really saying that the conduction electrons more around easily but resist being pushed closer to one another.

The oxygen you find in air (O₂) or water (H₂O) are all identical, but the people around you each has a different face. This contrasting situation used to amaze me! Do you realise that, without quantum mechanics, we would not understand why every oxygen atom usually has the same shape and size? The “quantum” explanation is that many properties of matter actually assume discrete values, equal to integral multiples of some relevant unit (the quantum); in everyday world they seem to vary continuously, merely because the steps escape notice, like a digital image appears to display smooth contrast just because one bit (the quantum for this case) is tiny compared to its entire range in tone.

Thus, when electrons (e) move in a magnetic field (B) they revolve in circular orbits due to the force of B on any particle with an electric charge, but the energy of these orbits is allowed only discrete values (see figure). What Tsui Chye and his colleagues discovered is that, at a low temperature, these electrons move together as a collective whole in a coordinated manner, forming an incompressible fluid i.e. liquid, and arising from the quantisation of their energies in the magnetic field, they behave as if some of them carry each a fraction (instead of a multiple) of the electric charge on an electron!

The discovery of Tsui and others show that many interacting individuals can imply the emergence of smaller entities! It is an example of the infinite richness of nature. Although we might one day come to know the basic laws of science almost completely, like the regularities of motion for electrons in a periodic potential added to a magnetic field, surprises a wait us at every level of higher organizations, such as: electrons in a solid, electrons in a solid inside a magnetic filed, electrons in a solid inside an intense magnetic field, electrons in a solid and intense field at ultralow temperature, electrons in a solid… with local variations in potential due to impurities, Who knows what more!