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Super ConductorsSuper Conductors

CONTENTSCONTENTS DefinitionDefinition Discovery of SuperconductivityDiscovery of Superconductivity Science of SuperconductivityScience of Superconductivity Cooper Pair Cooper Pair Meissner EffectMeissner Effect Types of superconductersTypes of superconducters Critical Temperature of some Critical Temperature of some

SuperconductorsSuperconductors Josephson EffectJosephson Effect ApplicationsApplications

Definition?????Definition????? For some materials, the resistivity vanishes at For some materials, the resistivity vanishes at

some low temperature; they become some low temperature; they become Superconductive. Superconductors have the Superconductive. Superconductors have the ability to conduct electrical current with ability to conduct electrical current with nono resistanceresistance(!!!), thus no loss of energy.(!!!), thus no loss of energy.

Discovery of SuperconductivityDiscovery of Superconductivity

Superconductivity was first discovered in 1911 by Superconductivity was first discovered in 1911 by the the Dutch physicist,Heike Kammerlingh OnnesDutch physicist,Heike Kammerlingh Onnes..

Onnes passed a current through a very pure Onnes passed a current through a very pure mercury wire and measured its resistance as he mercury wire and measured its resistance as he steadily lowered the temperature. Much to his steadily lowered the temperature. Much to his surprise there was no resistance at 4.2K.surprise there was no resistance at 4.2K.

The DiscoveryThe Discovery

At 4.2K, the Electrical Resistance Vanished.At 4.2K, the Electrical Resistance Vanished. Meaning Extremely Good Conduction of Meaning Extremely Good Conduction of

Electricity-SuperconductivityElectricity-Superconductivity

Science of SuperconductivityScience of Superconductivity The behavior of electrons inside a superconductor The behavior of electrons inside a superconductor

is vastly different. is vastly different.

The impurities and lattice framework are still The impurities and lattice framework are still there, but the movement of the superconducting there, but the movement of the superconducting electrons through the obstacle course is quite electrons through the obstacle course is quite different. different.

Because they bump into nothing and create no Because they bump into nothing and create no friction they can transmit electricity with no friction they can transmit electricity with no appreciable loss in the current and no loss of appreciable loss in the current and no loss of energy.energy.

The Science…The Science… A metal can be imagined as a lattice of positive A metal can be imagined as a lattice of positive

ions. Electrons moving through the lattice constitute ions. Electrons moving through the lattice constitute an electric current. an electric current.

Normally, the electrons repel each other and are Normally, the electrons repel each other and are scattered by the lattice, creating resistance.scattered by the lattice, creating resistance.

In superconductors, the flow of electrons is also In superconductors, the flow of electrons is also different. different.

It was first explained by BCS theory.It was first explained by BCS theory. The BCS theory realized that atomic lattice The BCS theory realized that atomic lattice

vibrations forced the electrons to pair up into teams vibrations forced the electrons to pair up into teams ((COOPER PAIRSCOOPER PAIRS)) that could pass all of the that could pass all of the obstacles which caused resistance in the conductor.obstacles which caused resistance in the conductor.

Cooper Pair :Cooper Pair : Two electrons that appear to "team up" in Two electrons that appear to "team up" in

accordance with theory - BCS or other - despite accordance with theory - BCS or other - despite the fact that they both have a negative charge the fact that they both have a negative charge and normally repel each other. and normally repel each other.

Below the superconducting transition Below the superconducting transition temperature, paired electrons form a condensate temperature, paired electrons form a condensate and start to flow without resistance. This pairing and start to flow without resistance. This pairing is caused by an attractive force between is caused by an attractive force between electrons from the exchange of phonons. electrons from the exchange of phonons.

Animation of Cooper pairsAnimation of Cooper pairs

The Science….The Science…. The superconducting state is defined by three The superconducting state is defined by three

very important factors: critical temperature (T), very important factors: critical temperature (T), critical field (critical field (H)H), and critical current density (J). , and critical current density (J). Each of these parameters is very dependant on Each of these parameters is very dependant on the other two properties presentthe other two properties present• critical temperature (T)critical temperature (T) The highest The highest

temperature at which superconductivity occurs in a temperature at which superconductivity occurs in a material. Below this transition temperature material. Below this transition temperature T T the the resistivity of the material is equal to zero.resistivity of the material is equal to zero.

• critical magnetic field (H)critical magnetic field (H) Above this value of Above this value of an externally applied magnetic field a superconductor an externally applied magnetic field a superconductor becomes nonsuperconducting.becomes nonsuperconducting.

• critical current density (J)critical current density (J) The maximum value The maximum value of electrical current per unit of cross-sectional area that of electrical current per unit of cross-sectional area that a superconductor can carry without resistance.a superconductor can carry without resistance.

Meissner EffectMeissner Effect

T > Tc

Superconductors have negative susceptibility. Superconductors have negative susceptibility. If a superconductor is cooled below its critical If a superconductor is cooled below its critical

temperature while in a magnetic field, the magnetic field temperature while in a magnetic field, the magnetic field surrounds but does not penetrate the superconductor. surrounds but does not penetrate the superconductor. The magnet induces current in the superconductor which The magnet induces current in the superconductor which creates a counter-magnetic force that causes the two creates a counter-magnetic force that causes the two materials to repel.materials to repel.

T < Tc

Levitation of a magnet above a Levitation of a magnet above a cooled superconductor cooled superconductor

Types of Superconductors:Types of Superconductors: Superconductors can be divided into two classes Superconductors can be divided into two classes

1.1. Type I Superconductors: Type I Superconductors: superconductivity is abruptly superconductivity is abruptly destroyed when the strength of the applied field rises above destroyed when the strength of the applied field rises above a critical value H. Most pure elemental superconductors, a critical value H. Most pure elemental superconductors, except niobium, technetium, vanadium and carbon except niobium, technetium, vanadium and carbon nanotubes, are Type I.nanotubes, are Type I.

2.2. Type II Superconductors: Type II Superconductors: In Type II superconductors, In Type II superconductors, raising the applied field past a critical value Hc1 leads to a raising the applied field past a critical value Hc1 leads to a mixed state (also known as the vortex state) in which an mixed state (also known as the vortex state) in which an increasing amount of magnetic flux penetrates the material, increasing amount of magnetic flux penetrates the material, but there remains no resistance to the flow of electric current but there remains no resistance to the flow of electric current as long as the current is not too large. At a second critical as long as the current is not too large. At a second critical field strength Hc2, superconductivity is destroyed. almost all field strength Hc2, superconductivity is destroyed. almost all impure and compound superconductors are Type II.impure and compound superconductors are Type II.

Critical Temperature of some Critical Temperature of some SuperconductorsSuperconductors

MaterialMaterial Critical Temp. (K)Critical Temp. (K) YY 0.010.01 AlAl 1.201.20 HgHg 4.154.15 Pb Pb 7.207.20 Nb3SnNb3Sn 18.0018.00 LaBaCuOLaBaCuO 40.0040.00 YBCuOYBCuO 92.0092.00

BiSr2Ca2Cu3Ox 113.00113.00 HgBaCaCuO 134.00134.00

Josephson EffectJosephson Effect The Josephson effect is the phenomenon of The Josephson effect is the phenomenon of

supercurrent to flow across the insulators(!!).supercurrent to flow across the insulators(!!). If an insulator is sandwitched between one If an insulator is sandwitched between one

superconductor & one normal conductor (or two superconductor & one normal conductor (or two superconductors), at some voltage,current flows superconductors), at some voltage,current flows due to due to tunneling of cooper pair.tunneling of cooper pair.

ApplicationsApplications Today superconductivity is being applied to many Today superconductivity is being applied to many

diverse areas such as: medicine, theoretical and diverse areas such as: medicine, theoretical and experimental science, the military, transportation, experimental science, the military, transportation, power production, electronics as well as many power production, electronics as well as many other areas. other areas.

Magnetically Levitated Trains Magnetically Levitated Trains (MagLev)(MagLev)

The track are made with a continuous series of vertical coils of wire The track are made with a continuous series of vertical coils of wire mounted inside. The wire in these coils is not a superconductor.mounted inside. The wire in these coils is not a superconductor.

As the train passes each coil, the motion of the superconducting As the train passes each coil, the motion of the superconducting magnet on the train induces a current in these coils, making them magnet on the train induces a current in these coils, making them electromagnets.The electromagnets on the train and outside electromagnets.The electromagnets on the train and outside produce forces that levitate the train and keep it centered above produce forces that levitate the train and keep it centered above the track.the track.

MagLev uses Electromagnetic Propulsion.MagLev uses Electromagnetic Propulsion. Trains are thrust forward by positively and Trains are thrust forward by positively and

negatively charged magnets.negatively charged magnets. The train floats on a cushion of air The train floats on a cushion of air

eliminating friction.eliminating friction.

Application in MedicalApplication in Medical

MRI (Magnetic Resonance Imaging) scans produce detailed images of soft tissues.

The superconducting magnet coils produce a

large and uniform magnetic field inside the patient's body.

Application in PowerApplication in Power

The cable configuration features a conductor made

from HTS wires wound around a flexible hollow core. Liquid nitrogen flows through the core, cooling the HTS

wire to the zero resistance state.

The conductor is surrounded by conventional dielectric insulation. The efficiency of this design reduces losses.

Economic Impact of Economic Impact of Superconducting EquipmentSuperconducting Equipment

• UtilitiesUtilities• Higher density transmission & higher Higher density transmission & higher

economic productivityeconomic productivity• Reduced environmental impactReduced environmental impact

• IndustrialIndustrial More cost effective industrial processes:More cost effective industrial processes:

• Manufacturing & energy production Manufacturing & energy production • Electrical storage, transmission and expansionElectrical storage, transmission and expansion

• TransportationTransportationMore cost effective electrical transportation:More cost effective electrical transportation:• High Speed Rail & MAGLEV technologies High Speed Rail & MAGLEV technologies • Electric car / busElectric car / bus• ShipShip

Worldwide Market for Worldwide Market for SuperconductivitySuperconductivity

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$1,000

$2,000

$3,000

$4,000

$5,000

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1997 2000 2003 2010

New Electronics Applications

New Large Scale ApplicationsMagnetic Resonance Imaging

Reseach & Technological Development

Millions

The dream - “Tomorrow’s The dream - “Tomorrow’s Superconducting World”Superconducting World”

*Energy saving: Power cable, motor, generator*Energy saving: Power cable, motor, generator *Computing: 1000 times faster supercomputers*Computing: 1000 times faster supercomputers *Information Technology: much faster, wider band *Information Technology: much faster, wider band

communication communication *levitated trains*levitated trains *Magnetically launched space shuttle & moreover.*Magnetically launched space shuttle & moreover.

RefferencesRefferences ““Integrated Electronics”- Jacob Millman, Christos C. Integrated Electronics”- Jacob Millman, Christos C.

Halkias Halkias

““Superconductivity Elementary”- Keshav N ShrivastavaSuperconductivity Elementary”- Keshav N Shrivastava

““Superconductivity Fundamentals & Applications”-Superconductivity Fundamentals & Applications”- Prof. Dr. Werner Buckel, Prof. Dr. Reinhold KleinerProf. Dr. Werner Buckel, Prof. Dr. Reinhold Kleiner WEBSITES: WEBSITES: wikipediawikipedia osun.org.comosun.org.com teachers.web.cern.comteachers.web.cern.com hyperphysics.eduhyperphysics.edu nextbigfuture.comnextbigfuture.com

THANKS…THANKS…