Superconductivity

Branch : Computer

Roll No. Name

33 Rami Akash

Introduction

Superconductivity:

The state of any conductor at which a conductor offers zero resistance is known as super conductivity and the material which shows superconductivity is known as superconductor.e.g. ceramic materials(Insulators at room temperature)

Resis

tan

ce

Temperature0K

Conductors

Superconductors

 

Breakdown of superconductivitySuperconductivity of a material has been breakdown if;1. Temperature is

increases2. Current density is

increases3. Magnetic field

increases

H

J T

Meissner effect

Meissner effect is the phenomena of superconductors to opposing the magnetic field and vice versa.

Theories of super conductivity

LONDON THEORY -1935

GINZBURG-LANDAU THEORY – 1950

SCHRIEFFER THEORY BARDEEN, COOPER, - 1957

Classification of Superconductors

These can be classified on base of:1. Magnetic field2. Critical Temperature3. Materials4. Operational Theory (BCS Theory)

1. Classification by Magnetic field

Where;S – SuperconductivityN – Normal StateSN – Mixed State of Superconductivity and Normal State

   

2. Classification by Critical Temperature I – Low temperature

superconductivityThe critical temperature range for low temperature super conductors is:

II – High temperature

superconductivityThe critical temperature range for low temperature super conductors is:

3. Classification by Materials

Superconductor material classes include chemical elements (e.g. mercury or lead), alloys (such as niobium-titanium, germanium-niobium, and niobium nitride), ceramics (YBCO and magnesium diboride), or organic superconductors (fullerenes and carbon nanotubes).YBCO: Yttrium barium copper oxide

4. Operational Theory (BCS Theory)

According to BCS theory by Bardeen, Cooper and Schrieffer in 1957. In superconducting materials, below a certain critical temperature, an electron hitting an ion causes the lattice to vibrate like a bell. The vibration affects a nearby electron, causing it to be attracted to the first electron. The electrons bind together into so-called Cooper pairs, all of which share the same quantum state. This allows them to move as one, in a condensate, conducting current without resistance.

BY BCS Theory

1. The pairs of free electrons does couple through phonons are known as cooper pairs.

2. The energy of cooper pair is lower then the energy of two individual layers

3. The electrons in cooper pair have opposite spin so net spin of cooper pair is zero.

4. The electron is behave like bosons in super conductors.

Advantages

Can carry large quantities of energy without heat loss.

Able to generate strong magnetic fields.

Superconductors beneficial applications in medical imaging techniques.

New superconductive films may result in miniaturization .

Superconductors increased speed in computer chips.

Disadvantage

Superconducting materials conduct current at only given temperature known as transition temperature.

Superconductors still do not show up in most everyday electronics.

Use of Superconductors

The superconductors are mainly used in:

Super conducting speaker

Magnetically levitating

trains

MRI(Magnetic Resonance Imaging) Scan