Electron cyclotron resonance
Encyclopedia : E : EL : ELE : Electron cyclotron resonance
Electron cyclotron resonance is a phenomenon observed both in plasma physics and condensed matter physics. An electron in a static and uniform magnetic field will move in a circle due to the Lorentz force. The circular motion may be superimposed with a uniform axial motion, resulting in a helix, or with a uniform motion perpendicular to the field, e.g., in the presence of an electrical or gravitational field, resulting in a cycloid. The frequency of this cyclotron motion is given (in SI units) by
- [\omega_=\frac].
In plasma physics
An ionized plasma may be efficiently produced or heated by superimposing a static magnetic field and a high-frequency electromagnetic field at the electron cyclotron resonance frequency. In the toroidal magnetic fields used in magnetic fusion energy research, the magnetic field decreases with the major radius, so the location of the power deposition can be controlled within about a centimeter. Furthermore, the heating power can be rapidly modulated and is deposited directly into the electrons. These properties make electron cyclotron heating a very valuable research tool for energy transport studies. In addition to heating, electron cyclotron waves can be used to drive current. The inverse process of electron cyclotron emission can be used as a diagnostic of the radial electron temperature profile.
In condensed matter physics
Within a solid the mass in the cyclotron frequency equation above is replaced with the effective mass tensor [\beginm^*\end]. Cyclotron resonance is therefore a useful technique to measure effective mass and Fermi surface cross-section in solids. In a sufficiently high magnetic field at low temperature in a relatively pure material
[\begin\omega_ > 1/\tau \\\hbar \omega_ > k_B T \\\end]
where [\tau] is the carrier scattering lifetime, [k_B] is Boltzmann's constant and [T] is temperature. When these conditions are satisfied, an electron will complete its cyclotron orbit without engaging in a collision, at which point it is said to be in a well-defined [Landau level].
See also
- Cyclotron
- Synchrotron
- Gyrotron
- ["Personal Reminiscences of Cyclotron Resonance,"] G. Dresselhaus, Proceedings of ICPS-27 (2004). This paper describes the early history of cyclotron resonance in its heyday as a band structure determination technique.
From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.