 Quantum Hall effect

The quantum Hall effect (or integer quantum Hall effect) is a quantum-mechanical version of the Hall effect, observed in two-dimensional electron systems subjected to low temperatures and strong magnetic fields, in which the Hall conductance undergoes quantum Hall transitions to take on the quantized values at certain level

where is the channel current, is the Hall voltage, is the elementary charge and is Planck's constant.The prefactor is known as the filling factor, and can take on either integer () or fractional () values.