Influence of Static Magnetic Fields
In semiconductor physics, a wealth of new phenomena are obtained from the application of static external fields. Whereas the most striking phenomena arise in transport, the optical properties are also radically modified by static fields. As in the case of optical fields, the properties of a system subject to a static magnetic field are determined by the interaction of the particles with this field. This interaction gives rise to the formation of new eigenstates at the one- or two-particle level, which in turn results in a direct response to the magnetic field as well as in a modified response to other external perturbations, such as optical fields. We shall not discuss the first aspect, which concerns the magnetic properties of the system, but instead shall focus on the second aspect in this chapter. Classically, charged particles orbit around the magnetic-field axis, in the case of free electrons with the cyclotron frequency w c 0 = eB/m.1 The corresponding confinement of the motion in quantum mechanics leads asymptotically (for large fields) to one-dimensional behavior in bulk semiconductors and is zero-dimensional for quantum wells in a perpendicular field. Both cases share many features with one- and zero-dimensional material systems, which can be realized in quantum wires and quantum dots, respectively. The analogy is indeed very close as long as we consider properties for which the center-of-mass motion of electron-hole pairs is negligible, an assumption usually valid for optical transitions.
KeywordsStatic Magnetic Field Landau Level Lower Landau Level Magnetie Field Coherent Pair State
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