Everything about Fermi Surface totally explained
In
condensed matter physics, the
Fermi surface is an abstract boundary useful for predicting the thermal, electrical, magnetic, and optical properties of
metals,
semimetals, and doped
semiconductors. The shape of the Fermi surface is derived from the periodicity and symmetry of the
crystalline lattice and from the occupation of
electronic energy bands. The existence of a Fermi surface is a direct consequence of the
Pauli exclusion principle, which allows a maximum of one electron per quantum state.
Theory
Formally speaking, the Fermi surface is a surface of constant energy in
. Thus the determination of the periods of oscillation for various applied field directions allows mapping of the Fermi surface.
Observation of the dHvA and SdH oscillations requires magnetic fields large enough that the circumference of the cyclotron orbit is smaller than a
mean free path. Therefore dHvA and SdH experiments are usually performed at high-field facilities like the
High Field Magnet Laboratory
in Netherlands,
Grenoble High Magnetic Field Laboratory in France, the
Tsukuba Magnet Laboratory in Japan or the
National High Magnetic Field Laboratory in the United States.
Angle resolved photoemission. The most direct experimental technique to resolve the electronic structure of crystals in the momentum-energy space (see
reciprocal lattice), and, consequently, the Fermi surface, is the
angle resolved photoemission spectroscopy (
ARPES). An example of the
Fermi surface of superconducting cuprates measured by
ARPES is shown in figure.
Two photon positron annihilation. With
positron annihilation the two photons carry the momentum of the electron away; as the momentum of a thermalized positron is negligible, in this way also information about the momentum distribution can be obtained. Because the positron can be
polarized, also the momentum distribution for the two
spin states in magnetized materials can be obtained. Another advantage with De Haas-Van Alphen-effect is that the technique can be applied to non-dilute alloys. In this way the first determination of a
smeared Fermi surface in a 30% alloy has been obtained in 1978.
Further Information
Get more info on 'Fermi Surface'.
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