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Topic: Quantum Hall effect

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	Quantum Hall effect -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-18)
		In the "ordinary" quantum Hall effect, known as the integer quantum Hall effect, ν takes on (Any of the natural numbers (positive or negative) or zero) integer values (ν = 1, 2, 3, etc.).
		The quantum Hall effect also provides an extremely precise independent determination of the (Click link for more info and facts about fine structure constant) fine structure constant, a quantity of fundamental importance in (A relativistic quantum theory of the electromagnetic interactions of photons and electrons and muons) quantum electrodynamics.
		The effect was explained by Laughlin in 1983, using a novel quantum liquid (Any distinct time period in a sequence of events) phase that accounts for the effects of interactions between electrons.
	www.absoluteastronomy.com /encyclopedia/Q/Qu/Quantum_Hall_effect.htm (464 words)

	Bell Labs: The Fractional Quantum Hall Effect (Site not responding. Last check: 2007-10-18)
		In 1879, Edwin Hall, a graduate student at Johns Hopkins University, discovered that, when a magnetic field was applied perpendicularly to a thin metal sheet that was conducting current, a small electrical voltage appeared that was perpendicular to both the sheet and the magnetic field.
		The Hall voltage and Hall resistance (the ratio of the Hall voltage to the current) are now commonly used in physics laboratories to measure the strengths of magnetic fields, as well as charge densities in various metals.
		This "anomalous" effect took the physics community by surprise and came to be known as the fractional quantum Hall effect.
	www.bell-labs.com /news/1998/october/13/2.html (719 words)

	Theory Group : Quantum Hall effect, Spin-excitons and Skyrmions
		The helicon is a circularly polarised electromagnetic branch with a dispersion inversely proportional to the Hall conductivity.
		I.D. Vagner and D.J. Bergman ''RF Quantum Hall Effect in a Superlattice''.
		Accordingly, in the paper [6] the effect of non-magnetic impurity scattering on the Landau level width in a quasi-two-dimensional conductor was studied.
	www.magniel.com /group/r_qhe.html (3127 words)

	Hall Effect
		The transverse voltage (Hall effect) measured in a Hall probe has its origin in the magnetic force on a moving charge carrier.
		The Hall effect is a conduction phenomenon which is different for different charge carriers.
		The Hall effect can be used to measure the average drift velocity of the charge carriers by mechanically moving the Hall probe at different speeds until the Hall voltage disappears, showing that the charge carriers are now not moving with respect to the magnetic field.
	hyperphysics.phy-astr.gsu.edu /hbase/magnetic/hall.html (380 words)

	What's Physics Good For?
		The Hall effect is used to determine the charge (+ or -) of the carriers of electric current and the speed with which they move through the material.
		In this case the resistance is quantized and the effect is called the quantum Hall effect (qhe).
		The quantum Hall effect is explained by noting that at these low temperatures, the electrons are trapped to move on a plane surface, in only two dimensions.
	curie.umd.umich.edu /Phys/classes/p150/archive/goodfor/fqhe.htm (782 words)

	Quantum Hall effect
		The quantum Hall effect (QHE) is the quantization of the Hall resistance, which may be observed in the presence of large magnetic field strength and low temperature.
		In a typical QHE experiment, a MOSFET is subjected to a large magnetic field of order 15 T, at a temperature of order 1 K.
		The quantum Hall effect was also used as an independent determination of the fine structure constant in quantum electrodynamics.
	www.brainyencyclopedia.com /encyclopedia/q/qu/quantum_hall_effect.html (357 words)

	Press Release: The 1998 Nobel Prize in Physics (Site not responding. Last check: 2007-10-18)
		The Hall effect can be used to determine the density of charge carriers (negative electrons or positive holes) in conductors and semi-conductors, and has become a standard tool in physics laboratories the world over.
		In their refined experimental studies of the quantum Hall effect, using among other things lower temperatures and more powerful magnetic fields, Störmer, Tsui and their co-workers found to their great surprise a new step in the Hall resistance which was three times higher than von Klitzing's highest.
		The discovery and the explanation of the fractional quantum Hall effect in 1982-83 may be said to represent an indirect demonstration of the new quantum fluid and its fractionally charged quasiparticles.
	nobelprize.org /physics/laureates/1998/press.html (1719 words)

	The Fractional Quantum Hall Effect -- Schedule
		The Non Commutative Geometry of the Integer Quantum Hall Effect, 1.
		The Non Commutative Geometry of the Integer Quantum Hall Effect, 2.
		The Non Commutative Geometry of the Integer Quantum Hall Effect, 3.
	www.physics.adelaide.edu.au /itp/workshops/fqHe_prog.html (176 words)

	Quantum Hall Effect (Site not responding. Last check: 2007-10-18)
		Plateau transition in the quantum Hall effect: Experiments on temperature and fr...
		The breakdown of the integer quantum Hall effect: a...
		Theory of electron-phonon interaction in the quantum Hall regime...
	www.scienceoxygen.com /phys/303.html (251 words)

	Quantum Hall effect gets new dimensions (October 2001) - News - PhysicsWeb (Site not responding. Last check: 2007-10-18)
		The quantum Hall effect is observed when the resistance of a two-dimensional gas of electrons is measured in a magnetic field.
		This integer quantum Hall effect could be explained without electron correlations, but this conventional approach failed when the fractional quantum Hall effect was discovered in 1982.
		When Zhang and Hu extended the theory of the quantum Hall effect to four dimensions, they found that the equations that described excitations at the boundary of the system were similar to Maxwell’s equations of classical electromagnetism, and also to the linear version of Einstein’s General Theory of Relativity.
	physicsweb.org /article/news/5/10/17 (575 words)

	LNE, Quantum metrological : quantum hall effect, Research and Development
		Over the last 20 years, work on the quantum effects of electron transport has shown the feasibility of replacing material standards with more stable and reproducible quantum standards and has made quantum electrical metrology possible.
		Since the quantum phenomena involved are observed in specific experimental conditions, special cryogenic current comparators (CCCs) have been developed at the Laboratory.
		A quantum current standard (based on the single-electron tunnelling effect) is also being finalized in the context of the metrological triangle experiment, which consists in developing a quantum Ohm's law from the three effects (JE, QHE and SET).
	www.lne.fr /en/r_and_d/electrical_metrology/quantum_electrical_metrology.shtml (341 words)

	History (Site not responding. Last check: 2007-10-18)
		The Hall effect was discovered by Edwin Hall in 1879 when he was a graduate student in the Johns Hopkins University under the advisory of Professor Henry A. Rowland, after whose name this department is named now.
		The first inversion layer Hall conductivity measurements in strong magnetic fields were done by S.Kawaji and his colleagues in 1975.
		Five years later, in 1985, Klaus von Klitzing was awarded Nobel Prize in Physics for the discovery of quantum Hall effect.
	www.pha.jhu.edu /~qiuym/qhe/node1.html (283 words)

	CSS - CSS Update, Volume 4, Number 5, The Quantum Goes Fractal
		He was actually using the Hall effect to characterize the transistor in a high magnetic field at very low temperature.
		The quantum Hall effect is now used to generate the standard of electrical resistance which is needed to calibrate sensitive electronic test equipment.
		Kirczenow's theory, developed together with post-doctoral fellows Brad Johnson, Crispin Barnes, and Richard Akis, shows that a fractal quantum Hall effect should be possible using single-electron quantum math, without invoking the many-body wave functions that were previously believed to be the only route to fractional quantum Hall plateaus.
	css.sfu.ca /update/vol4/4.5-kirczenov.html (1126 words)

	Classical Hall Effect
		The Hall conductance is derived to be a cyclic 2-cocycle on the algebra of observables and its expression resembles a generalized Kubo formula.
		Under the assumption that the Fermi level is in a spectral gap of the Hamiltonian, we establish that the Hall conductance is an integer mutiple of orbifold Euler characteristics of cocompact Fuchsian groups, and is therefore topological in character as well as fractional valued.
		Quantum Hall Effect on the Hyperbolic Plane in the presence of disorder,
	www-math.mit.edu /~vmathai/qheweb.html (321 words)

	Quantum mechanics and quantum Hall effect on Riemann surfaces - Iengo, Li (ResearchIndex) (Site not responding. Last check: 2007-10-18)
		We explicitly construct the wave functions of ground states in the case of a metric proportional to the Chern form of the `-bundle, and the wave functions of the Landau levels in the case of the the Poincar'e metric.
		R.Iengo and D.Li, Quantum mechanics and quantum Hall effect on Riemann surfaces, Nucl.
		10 The Quantum Hall Effect (context) - Prange, Girvin - 1990
	citeseer.ist.psu.edu /iengo94quantum.html (435 words)

	Read about Quantum Hall effect at WorldVillage Encyclopedia. Research Quantum Hall effect and learn about Quantum Hall ... (Site not responding. Last check: 2007-10-18)
		The quantum Hall effect is a quantum mechanical version of the Hall effect, observed in two-dimensional systems of
		The integer quantization of the Hall conductance was originally predicted by Ando, Matsumoto, and Uemura in
		The effect was explained by Laughlin in 1983, using a novel quantum liquid
	encyclopedia.worldvillage.com /s/b/Von_Klitzing_constant (450 words)

	Luttinger Liquids and the Quantum Hall Effect
		In the fractional quantum Hall effect the quantization is a consequence of the highly correlated state of the electron gas.
		While a quantum wire must be extremely clean to observe Luttinger liquid effects, the quantum Hall edge states are relatively insensitive to disorder.
		The analog of the single impurity in a quantum wire is a quantum point contact in the quantum Hall effect, shown in the figure above.
	dept.physics.upenn.edu /~mele/qcmt/p3.1/project.html (837 words)

	Relativistic Quantum Hall Effect (Site not responding. Last check: 2007-10-18)
		This effect is a version of the Quantum Hall Effect, which describes an influence of gravitation in Hall resistance.
		This effect could be used to measure the value of the gravity constant.
		To measure the Quantum Hall Effect in a gravity field, we consider a resting experiment facility e.g.
	www.tilmannschneider.de /rqhe_en.html (246 words)

	RMK articles : Jan Post on Topology and the Quantum Hall Effect
		The dominant theories about the fractional effect have led to associations with fractional charge, yet without a commitment whether it is to be taken per charge carrier or collectively in terms of unexplained open spots in the charge carrying lattice.
		It shows the quantum Hall effect is governed by the ratio of two quantum numbers: the flux state n of the cyclotron states and the (even) number of circulating electrons accumulating in the same cyclotron state.
		A125, 225 (1987); quantum Hall effect as a key to identify inadequacies of the Copenhagen interpretation.
	www22.pair.com /csdc/pd2/pd2fre36.htm (1607 words)

	Deutsches Museum Bonn: Exponate: Quantum Hall effect (Site not responding. Last check: 2007-10-18)
		The quantum Hall effect was »born« at about 2 o' clock in the morning on 5 February 1980.
		Sample of silicon on which the quantum Hall effect was verified by Klaus v.
		The voltage signals at the Hall contacts provide information on the concentration of mobile electrons, which is affected by the gate voltage.
	www.deutsches-museum-bonn.de /exponate/quanten-hall-effekt/quanten_hall_e.html (530 words)

	Hall effect -- Britannica Student Encyclopedia (Site not responding. Last check: 2007-10-18)
		The electric field, or Hall field, is a result of the force that the magnetic field exerts on the moving positive or...
		Derived from the taproom concerts given in city taverns in England during the 18th and 19th centuries, music hall entertainment was eventually confined to a stage, with the audience seated at tables; liquor sales paid the...
		Factsheet on the effects of ozone depletion on humans, plants, and marine life, with the increase in the ultraviolet rays that are emitted from the Sun.
	www.britannica.com /ebi/article-9325602 (817 words)

	Quantum Hall effect (Site not responding. Last check: 2007-10-18)
		The quantum Hall effect (QHE) is the quantization of the Hall resistance, which may beobserved in the presence of large magnetic field strength and low temperature.
		In a typical QHE experiment, a MOSFET is subjected to a large magnetic field oforder 15 T, at a temperature of order 1 K.There is a two-dimensional electron gas maintained in the inversion layer of theMOSFET, the plane of which is aligned perpendicular to the magnetic field.
		In 1990, theInternational System of Units (SI) redefined the Ohm interms of the QHE, with the accepted value of the quantum Hall resistance (or von Klitzing constant, after theeffect's discoverer).
	www.therfcc.org /quantum-hall-effect-24224.html (312 words)

	Quantum Hall Effect Systems
		We investigated the magneto-roton instability of the incompressible quantum Hall liquid in higher Landau levels (LLs) at a partial filling nubar=1/(2s+1) of the last LL n, with integral s.
		Impurity effects further lower the energy of the electron-solids because by deformation, these phases are better adapted to follow an underlying electrostatic potential than is an incompressible, homogeneous quantum-liquid.
		One flux quantum remains free again, and the effective filling is one, in analogy with the case of CFs of the first generation.
	www.unifr.ch /phystheo/QHES.html (1273 words)

	Edge current channels and Chern numbers in the integer quantum Hall effect - Kellendonk, Richter, Schulz-Baldes ... (Site not responding. Last check: 2007-10-18)
		Under a gap condition on the corresponding planar model, this quantum number is shown to be equal to the quantized Hall conductivity as given by the Kubo-Chern formula.
		1 Absence of backscattering in the quantum Hall effect in mult..
		1 Anomalous Integer Quantum Hall Effect in the Ballistic Regim..
	citeseer.ist.psu.edu /kellendonk00edge.html (901 words)

	Fractional quantum Hall effects (March 2000) - Physics World - PhysicsWeb
		Although the integer and fractional quantum Hall effects were discovered in the early 1980s, they are still the focus of a large research effort worldwide, and many new phenomena have been discovered in recent years.
		In the classical effect, a thin strip of a conducting material is placed in a magnetic field and a current is driven through it.
		When the Hall effect is measured at low temperatures in a sample that is so thin that the electrons are confined to move only in the x-y plane, the Hall resistance is found to deviate from the classical behaviour.
	physicsweb.org /article/world/13/3/10/1 (617 words)

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