Bose Einstein Condensation Condensed Matter II –Spring 2007

Bose Einstein Condensation

• Condensed Matter II –Spring 2007

• Davi Ortega

Summary

• From counting to a new state of matter

• Indistinguishability of particles
• Counting indistinguishable particles
• Einstein’s conclusion = New State
• Some properties

• BEC in Dilute Gases and Liquid Helium

• Experiments to achieve the BEC.

• News

Statistics of Idea Gas

• Two Particles Gas: A and B.

Some Theory

More Theory

Two more useful results

An Last statement

• This whole theory assume non interacting particles: Schrödinger Equation

• Interacting Particles: Gross-Pitaeviski Eq.

Achievements

• 1938 – Pyotr Kapitsa John Allen and Don Misener: Helium 4

• 1995 – Eric Cornell and Carl Wieman: Rb87: Pure BEC.

• 1995 – Wolfgang Ketterle Na23. (4 months later)

Liquid He vs. Diluted Gas

• Strong Interactions in He qualitatively changes the nature of transition.

• Diluted Gas

• Pure Condensate state

• Liquid Helium

• Zero Viscosity
• And other strange properties.

How to make a BEC ?

• Heat the atoms: 600 K (gas)

• Confine them in a beam

• Decelerate the beam

• Trap the atoms (Magneto Optical Trap)

• Magnetic Trapping (avoid atoms recoil by spontaneous emission and random absorption)

• Evaporative Cooling

Famous Picture

Any other way ?!

Current Research

• BEC achieved in several atoms.

• Strange Properties:

• Superfluidity
• Slowing of light

• Wave-like phenomena in atoms.

• Interference between two condensates.

• Atom Laser

• Coherent Matter Waves