Shubnikov–de Haas effect

In solid-state physics of the Shubnikov - de Haas effect describes the oscillation of the electrical resistance of a pure single crystal as a function of a strong external magnetic field at low temperatures. Named after Lev Vasilyevich Shubnikov de Haas effect and hiking John based on the same physical principles as the de Haas -van Alphen - effect. In contrast, also to be resettled in this field quantum Hall effect describes a perpendicular to a current flow forming voltage.

The oscillations in the resistance in an externally applied magnetic field were first discovered in 1930 by the two names of bismuth donors. These results supported the predictions of the quantization of energy states in the magnetic field in the so-called Landau levels by experimental results.

At low temperatures and strong magnetic fields, the free electrons as quantum mechanical harmonic oscillators behave, that is, their energy levels are perpendicular to the magnetic field is quantized ( Landau level ). Under increasing magnetic field the distance between these levels increases, their position is shifted relative to the Fermi energy. If the Fermi energy while within a - broadened by electron-phonon collisions to form a band - is Landau levels, scattering of electrons is possible and the electrical resistance changes depending on the magnetic field. It is maximum when the Fermi level is in the middle of the level, since then the ratio of conduction electrons to free accessible by scattering states is just one. If the Fermi energy is located between two Landau levels, then the electrons, the energy gap to the next level can not be overcome due to the low temperature, diffusion is no longer possible, and the resistance decreases. A clear explanation is given in the framework of edge channel model.

The Shubnikov - de Haas effect (similar to the quantum Hall effect in some cases ) are used to determine certain material properties. Among them, the following:

  • Determination of the Fermi surface;
  • Determination of the charge carrier density ( from the frequency of oscillation );
  • Characterization of highly doped inhomogeneous structures ( occur several frequencies );
  • Determine the effective mass of the charge carriers (measured at two different temperatures );
  • Characterization of superlattice semiconductor structures.
Lev Shubnikov Wander Johannes de Haas De Haas–van Alphen effect Quantum harmonic oscillator Effective mass (solid-state physics)
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