In condensed matter physics, spin–charge separation is an unusual behavior of

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...

s in some materials in which they 'split' into three independent particles, the

spinon Spinons are one of three quasiparticles, along with holons and orbitons, that electrons in solids are able to split into during the process of spin–charge separation, when extremely tightly confined at temperatures close to absolute zero. The e ...

, the

orbiton Orbitons are one of three quasiparticles, along with holons and spinons, that electrons in solids are able to split into during the process of spin–charge separation, when extremely tightly confined at temperatures close to absolute zero. The e ...

and the holon (or chargon). The electron can always be theoretically considered as a

bound state Bound or bounds may refer to: Mathematics * Bound variable * Upper and lower bounds, observed limits of mathematical functions Physics * Bound state, a particle that has a tendency to remain localized in one or more regions of space Geography * ...

of the three, with the spinon carrying the spin of the electron, the

carrying the orbital degree of freedom and the chargon carrying the

charge Charge or charged may refer to: Arts, entertainment, and media Films * '' Charge, Zero Emissions/Maximum Speed'', a 2011 documentary Music * ''Charge'' (David Ford album) * ''Charge'' (Machel Montano album) * ''Charge!!'', an album by The Aqu ...

, but in certain conditions they can behave as independent

quasiparticles In physics, quasiparticles and collective excitations are closely related emergent phenomena arising when a microscopically complicated system such as a solid behaves as if it contained different weakly interacting particles in vacuum. For exa ...

. The theory of spin–charge separation originates with the work of Sin-Itiro Tomonaga who developed an approximate method for treating one-dimensional interacting quantum systems in 1950. This was then developed by

Joaquin Mazdak Luttinger Joaquin (Quin) Mazdak Luttinger (December 2, 1923 – April 6, 1997) was an American physicist well known for his contributions to the theory of interacting electrons in one-dimensional metals (the electrons in these metals are said to be in ...

in 1963 with an exactly solvable model which demonstrated spin–charge separation. In 1981 F. Duncan M. Haldane generalized Luttinger's model to the Tomonaga–

Luttinger liquid A Luttinger liquid, or Tomonaga–Luttinger liquid, is a theoretical model describing interacting electrons (or other fermions) in a one-dimensional conductor (e.g. quantum wires such as carbon nanotubes). Such a model is necessary as the commo ...

concept whereby the physics of Luttinger's model was shown theoretically to be a general feature of all one-dimensional metallic systems. Although Haldane treated spinless fermions, the extension to

spin-½ In quantum mechanics, spin is an intrinsic property of all elementary particles. All known fermions, the particles that constitute ordinary matter, have a spin of . The spin number describes how many symmetrical facets a particle has in one full ...

fermions and associated spin–charge separation was so clear that the promised follow-up paper did not appear. Spin–charge separation is one of the most unusual manifestations of the concept of

quasiparticle In physics, quasiparticles and collective excitations are closely related emergent phenomena arising when a microscopically complicated system such as a solid behaves as if it contained different weakly interacting particles in vacuum. For exa ...

s. This property is counterintuitive, because neither the spinon, with zero charge and spin half, nor the chargon, with charge minus one and zero spin, can be constructed as combinations of the electrons, holes, phonons and

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they a ...

s that are the constituents of the system. It is an example of fractionalization, the phenomenon in which the quantum numbers of the quasiparticles are not multiples of those of the elementary particles, but fractions. The same theoretical ideas have been applied in the framework of

ultracold atom Ultracold atoms are atoms that are maintained at temperatures close to 0 kelvin (absolute zero), typically below several tens of microkelvin (µK). At these temperatures the atom's quantum-mechanical properties become important. To reach such low ...

s. In a two-component Bose gas in 1D, strong interactions can produce a maximal form of spin–charge separation.

Observation

Building on physicist F. Duncan M. Haldane's 1981 theory, experts from the Universities of Cambridge and

Birmingham Birmingham ( ) is a City status in the United Kingdom, city and metropolitan borough in the metropolitan county of West Midlands (county), West Midlands in England. It is the second-largest city in the United Kingdom with a population of 1. ...

proved experimentally in 2009 that a mass of electrons artificially confined in a small space together will split into spinons and holons due to the intensity of their mutual repulsion (from having the same charge).Discovery About Behavior Of Building Block Of Nature Could Lead To Computer Revolution
''Science Daily'' (July 31, 2009) A team of researchers working at the Advanced Light Source (ALS) of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory observed the peak spectral structures of spin–charge separation three years prior.

References

External links

Observation of Spin-Charge Separation in One-Dimensional SrCuO₂
{{DEFAULTSORT:Spin-Charge Separation Quasiparticles Condensed matter physics