Citizendia
Your Ad Here

In physics, a quasiparticle refers to a particle-like entity arising in certain systems of interacting particles. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made It can be thought of as a single particle moving through the system, surrounded by a cloud of other particles that are being pushed out of the way or dragged along by its motion, so that the entire entity moves along somewhat like a free particle. The quasiparticle concept is one of the most important in condensed matter physics, because it is one of the few known ways of simplifying the quantum mechanical many-body problem, and is applicable to an extremely wide range of many-body systems. Condensed matter physics is the field of Physics that deals with the macroscopic physical properties of Matter. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons The many-body problem may be defined as the study of the effects of interaction between bodies on the behaviour of a many-body system i

Contents

Description

In the language of many-body quantum mechanics, a quasiparticle is a type of low-lying excited state of the system (a state possessing energy very close to the ground state energy) that is known as an elementary excitation. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Excitation is an elevation in energy level above an arbitrary baseline energy state In Quantum mechanics, a stationary state is an Eigenstate of a Hamiltonian, or in other words a state of definite energy This means that most of the other low-lying excited states can be viewed as states in which multiple quasiparticles are present. It turns out that the interactions between quasiparticles become negligible at sufficiently low temperatures, in which case we can obtain a great deal of information about the system as a whole, including the flow properties and heat capacity, by investigating the properties of individual quasiparticles. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature A quantum fluid can refer to a cluster of Valence electrons moving together after they undergo fermionic condensation. Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the Temperature of a unit quantity

Actually, most many-body systems possess two types of elementary excitations. The first type, the quasiparticles, correspond to single particles whose motions are modified by interactions with the other particles in the system. The second type of excitation corresponds to a collective motion of the system as a whole. These excitations are called collective modes, and they include phenomena such as zero sound, plasmons, and spin density waves. Zero sound is the name given by Landau to the longitudinal density vibrations in quantum Fermi liquids In Physics, a plasmon is a quantum of a plasma oscillation The plasmon is the Quasiparticle resulting from the Quantization of Plasma oscillations Spin-density wave (SDW and charge-density wave (CDW are names for two similar low-energy ordered states of solids

The idea of quasiparticles originated in Landau's theory of Fermi liquids, which was originally invented for studying liquid helium-3. Lev Davidovich Landau ( Russian language: Ле́в Дави́дович Ланда́у ( January 22, 1908 &ndash April 1, 1968 Fermi liquid is a generic term for a quantum mechanical Liquid of Fermions that arises under certain physical conditions when the Temperature This article is about the elemental isotope For the record label Helium 3 see Muse or A&E Records. For these systems a strong similarity exists between the notion of quasi-particle and dressed particles in quantum field theory. In quantum field theory (QFT the forces between particles are mediated by other particles

The dynamics of Landau's theory is defined by a kinetic equation of the mean-field type. Kinetic theory (or kinetic theory of gases) attempts to explain Macroscopic properties of Gases such as pressure temperature or volume by considering A Many-body system with interactions is generally very difficult to solve exactly except for extremely simple cases ( Gaussian field theory, 1D Ising model. A similar equation, the Vlasov Equation, is valid for a plasma in the so-called plasma approximation, in which charged particles are considered moving in the electromagnetic field collectively generated by all other particles, and hard collisions between the charged particles are neglected. The Boltzmann equation, also often known as the Boltzmann transport equation, devised by Ludwig Boltzmann, describes the statistical distribution of In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound When a kinetic equation of the mean-field type is a valid first-order description of a system, second-order corrections determine the entropy production, and generally take the form of a Boltzmann-type collision term, in which figure only "far collisions" between virtual particles. A Many-body system with interactions is generally very difficult to solve exactly except for extremely simple cases ( Gaussian field theory, 1D Ising model. In Thermodynamics (a branch of Physics) entropy, symbolized by S, is a measure of the unavailability of a system ’s Energy The Boltzmann equation, also often known as the Boltzmann transport equation, devised by Ludwig Boltzmann, describes the statistical distribution of In other words, every type of mean-field kinetic equation, and in fact every mean-field theory, involves a quasi-particle concept. A Many-body system with interactions is generally very difficult to solve exactly except for extremely simple cases ( Gaussian field theory, 1D Ising model.

Note that the use of term quasiparticle seems to be ambiguous. Some authors use the term in order to distinguish them from real particles, others (including author of the above passage) to describe an excitation similar to a single particle excitation as opposed to a collective excitation. Both definitions mutually exclude each other as with the former definition collective excitations which are no "real" particles are considered to be quasiparticles. The problems arising from the collective nature of quasiparticles have also been discussed within the philosophy of science, notably in relation to the identity conditions of quasiparticles and whether or not they should be considered "real" by the standards of, for example, entity realism. Entity realism is a philosophical position within the debate about Scientific realism. [1][2]

Phonons are the quanta of classical sound waves and sound waves do not need the notion of atoms. In Physics, a phonon is a quantized mode of vibration occurring in a rigid crystal lattice, such as the Atomic lattice of a Solid Magnons are the quanta of classical spinwaves, which also do not need elementary spins. A magnon is a Collective excitation of the electrons ' spin structure in a Crystal lattice. Photons inside an isolator are the quanta of classical dressed electromagnetic waves and do not need the notion of electrons for the definition of the refractive index. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena Plasmons are the quanta of the plasma oscillations and they only need charge density and mass density and no electrons or ions. In Physics, a plasmon is a quantum of a plasma oscillation The plasmon is the Quasiparticle resulting from the Quantization of Plasma oscillations Plasma oscillations, also known as " Langmuir waves " (after Irving Langmuir) are rapid oscillations of the electron density in conducting media such as Polarons are the quanta of the oscillating polarization in a lightly doped semiconductor and also do not need elementary charge or mass. A polaron is a Quasiparticle composed of an Electron plus its accompanying polarization field.

In May 2008 Merav Dolev from the Weizmann Institute of Science in Israel, reported in Nature that his team had observed Quasiparticles in extremely pure gallium arsenide that have a fraction of the charge of an electron. Quasiparticles with one-quarter an electron charge were observed. Until now, researchers have only been able to form quasiparticles with one-third, one-fifth or one-seventh of the charge on an electron. [3]


Examples

See also

References

  1. ^ A. An electron hole is the conceptual and mathematical Opposite of an Electron, useful in the study of Physics and Chemistry. Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. A Many-body system with interactions is generally very difficult to solve exactly except for extremely simple cases ( Gaussian field theory, 1D Ising model. Gelfert, 'Manipulative Success and the Unreal', International Studies in the Philosophy of Science Vol. 17, 2003, 245-263
  2. ^ B. Falkenburg, Particle Metaphysics (The Frontiers Collection), Berlin: Springer 2007, esp. pp. 243-46
  3. ^ Cosmos magazine June 2008

External links


Further reading

Dictionary

quasiparticle

-noun

  1. (physics) Any entity that has some characteristics of a distinct particle, but comprises a grouping of multiple particles
© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
 Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic