The quantum Hall effect describes electron behavior in a magnetic field at low temperatures. It confirms quantum mechanics and is used to measure electrical resistance and study superconductors. The Hall effect, discovered in 1879, is when charge carriers scatter due to a magnetic field, creating a voltage difference. Physicists studied the Hall effect in thin plates and found sharp resistance peaks at specific energy levels, which are predictable and consistent. This led to the creation of resistance standards for testing electronics. The quantum Hall effect confirms the quantum nature of matter and was discovered in 1980 by Klaus von Klitzing, who won the Nobel Prize in Physics.
The quantum Hall effect is a well-accepted theory in physics that describes the behavior of electrons within a magnetic field at extremely low temperatures. The observations of the effect clearly confirm the theory of quantum mechanics as a whole. The results are so precise that the standard for measuring electrical resistance uses the quantum Hall effect, which is also the basis of work done on superconductors.
The Hall effect, discovered by Edwin Hall in 1879, is observed when a current of electricity passes through a conductor placed in a magnetic field. Charge carriers, which are usually electrons but can be protons, scatter on the side of the conductor due to the influence of the magnetic field. The phenomenon can be visualized as a series of cars being blown sideways by a strong wind as they travel along a highway. The cars take a curved path as they attempt to move forward but are forced sideways.
A potential difference develops between the sides of the conductor. The voltage difference is quite small and depends on the composition of the conductor. Signal amplification is necessary to make useful instruments based on the Hall effect. This imbalance in electric potential is the principle behind a Hall probe that measures magnetic fields.
With the popularity of semiconductors, physicists became interested in examining the Hall effect in plates so thin that charge carriers were essentially limited to motion in two dimensions. They applied current to conductive plates under strong magnetic fields and low temperatures. Instead of seeing electrons being pulled sideways in continuous curving paths, the electrons made sudden leaps. There were sharp peaks in the resistance to flow at specific energy levels as the magnetic field strength was changed. Between the peaks, the resistance dropped to near zero, a characteristic of low-temperature superconductors.
Physicists also realized that the energy level needed to cause a resistance peak was not a function of the composition of the conductor. The resistance peaks occurred at whole multiples of each other. These peaks are so predictable and consistent that tools based on the quantum Hall effect can be used to create resistance standards. These standards are essential for testing electronics and ensuring reliable performance.
The quantum theory of atomic structure, which is the concept that energy comes in discrete and whole packets at the subatomic level, predicted the quantum Hall effect as early as 1975. In 1980, Klaus von Klitzing was awarded the Nobel Prize in Physics for his discovery that the quantum Hall effect was in fact exactly discrete, meaning that electrons could exist only in sharply defined energy levels. The quantum Hall effect has become another argument for the quantum nature of matter.
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