Weird Fractional Quantum Hall Effect

In a recent publication to Physical Review Letters, "Optical Probing of the Spin Polarization of the v= 5/2 Quantum Hall State" the authors: M. Stern, P. Plochocka, V. Umansky, D. K. Maude, M. Potemski, and I. Bar-Joseph, describe a phenomena resulting in a pseudoparticle having non-integer charge!

This is all based on the fractional quantum Hall effect.

Recall the classical Hall effect, discovered by Edwin Hall in 1879. This effect occurs when you apply a magnetic field perpendicular to a current in a conductor, producing a voltage difference across the conductor. This voltage difference is sometimes called the Hall Voltage.

If you have a system of electrons in a plane (two-dimensional) or on a surface that are at low temperatures, you can produce Hall voltages of only quantized values by applying a strong magnetic field. This is the integer quantum Hall effect. You can calculate the Hall Resistance,

R= (h/e^2)/v

Where h is Planck's constant, e is the fundamental charge, and v is called the filling factor.

In some cases the electrons behave as if they are a fluid. In this case they behave as a pseudoparticle with fractional charge. Very interesting! This occurs when v is fractional, it is specifically interesting at v = 5/2.

I have not yet finished the letter, but something mysterious occurs at v = 5/2. There is a lot of interesting physics here!

George