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Name: Sid S.
Status: student
Grade: 9-12
Location: AZ
Country: N/A
Date: 7/12/2005


Question:
Does Hall Effect have to do with quantum spin number? If so, what kind of relationship does it have with the number?


Replies:
Sid,

The Hall Effect is not due to an electron's spin. It is due to the charge of an electron. When electrons MOVE THROUGH a magnetic field, perpendicular to the direction of the field, they are directed to the side, moving in a circle if possible. If they cannot move in a circle, they will at least move to the side. This is true for any moving electric charge.

Voltage is placed along a long metal strip, causing current to flow through it. The strip is inserted into a magnetic field. The moving electrons are then pushed toward only one side of the strip. This creates a voltage across the strip, from side to side. The direction of this voltage tells us whether the electrons have a positive charge or a negative charge.

Kenneth E. Mellendorf
Physics Instructor
Illinois Central College


The Hall effect as such involves charge carries and is a measurement involving current, voltage, and an external magnetic field. In the mid 1980's the paper by Von Klitzing, Dorda and Pepper discovered the quantum hall effect. The upshot of the effect was that the Hall voltage was multiples of the charge of the electron and Planck's constant. The multiples were attributed to Landau Levels, which involve spin in a magnetic field.

Several years following this discovery, the fractional quantum hall effect was discovered. The fractions seem to be an effect of graininess of the Landau Levels.

These are experiments performed at high magnetic fields (8-30T), low temperatures (50milliKelvin to 1.2 Kelvin) and using high purity samples.

Dr. Harold Myron



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