The chiral Battery

If you haven’t heard of the chiral battery, it’s because it hasn’t been invented yet. I first heard of the chiral effect while reading my son’s doctoral thesis. In it, he explains how neutron stars have all the elements required to generate the chiral current. Charbonneau says: “It is an unusual but beautiful pure, quantum phenomena that has no analogue in classical physics.” Indeed.

chiral battery

Neutron stars are the aftermath of supernovae. Most of the star is blown to bits but the neutrons that remain collapse into a tight ball with twice the mass of the sun and a diameter that could fit into Kamloops.

Neutron stars are so hot that the neutrons are boiled into a quarks/gluon soup. Gluons, as the name suggests, ordinarily hold the neutrons together except in this hellish version of Kamloops the quarks and gluons form a plasma. It’s in this plasma that the weird chiral effect takes place.

The word “chirality” might be familiar. The word derives from Greek for “handedness” and it’s expressed in different ways. Chirality is not the same as mirror image. For example, left hands are non-superposable mirror images of the right hand: no matter how the two hands are oriented, it is impossible for the features of both hands to coincide. Try it in a mirror.

In organic molecules, chirality is expressed by the way they are assembled. For some inexplicable reason, most organic molecules have the same chirality, perhaps imprinted that way from the big bang. In quark/gluon plasmas, it’s in the direction that particles spin.

Regardless of the exact means, all batteries depend on the separation of charge. The energy required to separate the charge can be from heat (thermocouple), light (solar), or any source that will turn copper windings through a magnetic field (wind, hydro, diesel, etc).

Charge separation in chiral batteries results from an uneven number of particles spinning in one direction compared to the opposite: the chirality is not zero. Over time, the numbers balance out but at any moment, randomness can tip the balance.  Fukushima et al explain: “In pure SU(N) Yang-Mills theory this process is completely random; the dynamics of the chirality change is that of a one-dimensional random walk.” At any specific moment, the plasma is unbalanced. “Hence, it is expected that every time the quark-gluon plasma is produced, it will possess a non-zero chirality.”

Once you have a non-zero chirality, the plasma is now primed and ready to produce a voltage. All that’s required is the application of an external magnetic field which will separate the charged particles. When current flows, the plasma is returned to a zero-chirality state but the plasma is in constant flux so the process repeats itself.

Since we can’t buy cans of quark/gluon plasma off the shelf, there has to be better way to make a battery. H. Torres-Silva suggests how. Instead of using plasma, use the semiconductor graphene. “Chirality in graphene is not related to the usual spin states considered above but instead refers to the sublattice states.”

Future electronics teachers will no doubt include chiral batteries in their lessons. Retired ones will just give their heads a shake.