The term Fermi point has two applications but refers to the same phenomena ( special relativity): *Fermi point (

quantum field theory In theoretical physics, quantum field theory (QFT) is a theoretical framework that combines classical field theory, special relativity, and quantum mechanics. QFT is used in particle physics to construct physical models of subatomic particles and ...

) *Fermi point (

nanotechnology Nanotechnology, also shortened to nanotech, is the use of matter on an atomic, molecular, and supramolecular scale for industrial purposes. The earliest, widespread description of nanotechnology referred to the particular technological goal o ...

) For both applications count that the symmetry between particles and anti-particles in weak interactions is violated:
At this point the particle energy E = cp is zero.
In nanotechnology this concept can be applied to electron behavior. An electron when as single particle is a

fermion In particle physics, a fermion is a particle that follows Fermi–Dirac statistics. Generally, it has a half-odd-integer spin: spin , spin , etc. In addition, these particles obey the Pauli exclusion principle. Fermions include all quarks an ...

obeying the Pauli exclusion principle.

Fermi point (quantum field theory)

Fermionic systems that have a Fermi surface (FS) belong to a

universality class In statistical mechanics, a universality class is a collection of mathematical models which share a single scale invariant limit under the process of renormalization group flow. While the models within a class may differ dramatically at finite s ...

. Any collection of fermions with weak repulsive interactions belongs to this class. At the Fermi point, the break of symmetry can be explained by assuming a vortex or singularity will appear as a result of the spin of a fermi particle ( quasiparticle, fermion) in one dimension of the three-dimensional momentum space.

Fermi point (nanoscience)

The Fermi point is one particular electron state. The Fermi point refers to an event

chirality Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from ...

of electrons is involved and the diameter of a

carbon nanotube A scanning tunneling microscopy image of a single-walled carbon nanotube Rotating single-walled zigzag carbon nanotube A carbon nanotube (CNT) is a tube made of carbon with diameters typically measured in nanometers. ''Single-wall carbon na ...

for which the nanotube becomes metallic. As the structure of a carbon nanotube determines the energy levels that the carbon's electrons may occupy, the structure affects macroscopic properties of the nanotube structure, most notably electrical and thermal conductivity. Flat graphite is a

conductor Conductor or conduction may refer to: Music * Conductor (music), a person who leads a musical ensemble, such as an orchestra. * ''Conductor'' (album), an album by indie rock band The Comas * Conduction, a type of structured free improvisation ...

except when rolled up into small cylinders. This circular structure inhibits the internal flow of electrons and the graphite becomes a semiconductor; a transition point forms between the valence band and

conduction band In solid-state physics, the valence band and conduction band are the bands closest to the Fermi level, and thus determine the electrical conductivity of the solid. In nonmetals, the valence band is the highest range of electron energies in w ...

. This point is called the Fermi point. If the diameter of the carbon nanotube is sufficiently great, the necessary transition phase disappears and the nanotube may be considered a conductor.

Notes

{{reflist Critical phenomena Nanoelectronics Condensed matter physics Quantum field theory Special relativity

Fermi point (quantum field theory)

Fermi point (nanoscience)

See also

Notes