Space Telescope Science Institute Title “When freezing cold is not cold enough - new forms of matter close to absolute zero temperature” Wolfgang Ketterle Massachusetts Institute of Technology MIT-Harvard Center for Ultracold Atoms 9/2/09 Meridian Lecture Space Telescope Science Institute Baltimore

The coldest matter in the universe What is energy Quantum Gases The coldest matter in the universe

One form of energy is motion (kinetic energy). What is temperature What is temperature? A measure of energy One form of energy is motion (kinetic energy).

Cold particles move slowly Hot particles are fast

What is the lowest temperatures possible?

What is temperature Zero degree Kelvin (-273 degrees Celsius, -460 degrees Fahrenheit) is the zero point for energy

The highest temperature is infinite (In principle it is possible for particles to have arbitrarily high kinetic energies – until they become so heavy (due to E=mc2) that they from a black hole – at the Planck temperature of 1032 K)

What is the difference in temperature between summer and winter? What is temperature What is the difference in temperature between summer and winter? 20 %

How cold is interstellar space? 3 K

What happens to atoms at low temperatures? Atom slow down What happens to atoms at low temperatures? They slow down 600 mph (300 m/sec) 1 cm/sec They march in lockstep

Molecule of the year Matter made of waves!

Molecule of the year

Laser beam and light bulb Photons/atoms moving randomly Photons/atoms are one big wave Ordinary light Laser light

Bose/Einstein * 1925

The concepts The cooling methods Laser cooling Evaporative cooling

Hot atoms

Hot atoms Laser beams

Hot atoms Fluorescence Laser beams

If the emitted radiation is blue shifted Fluorescence Laser beams If the emitted radiation is blue shifted (e.g. by the Doppler effect) ….

Cold atoms: 10 – 100 K Fluorescence Laser beams Chu, Cohen-Tannoudji, Phillips, Pritchard, Ashkin, Lethokov, Hänsch, Schawlow, Wineland …

MOT Laser cooling 2.5 cm

The concepts Evaporative cooling

Magnetic trap setup (GIF) Phillips et al. (1985) Pritchard et al. (1987)

Magnetic trap setup The condensate a puff of gas 100,000 thinner than air size comparable to the thickness of a hair magnetically suspended in an ultrahigh vacuum chamber

Guinness Book Record

WK and Dark SPOT Sodium laser cooling experiment (1992)

Sodium BEC I experiment (2001)

Evaporative cooling Dan Kleppner Tom Greytak Dave Pritchard

Current Research Cold molecules Cold fermions

Can electrons form a Bose-Einstein condensate and become superfluid (superconducting)? Two kinds of particles Bosons: Particles with an even number of protons, neutrons and electrons Fermions: odd number of constituents Only bosons can Bose-Einstein condense!

Can electrons form a Bose-Einstein condensate and become superfluid (superconducting)? Two kinds of particles Bosons: Particles with an even number of protons, neutrons and electrons Fermions: odd number of constituents Only bosons can Bose-Einstein condense! How can electrons (fermions) condense? They have to form pairs!

Can we learn something about superconductivity of electrons from cold atoms? Yes, by studying pairing and superfluidity of atoms with an odd number of protons, electrons and neutrons

Gallery of superfluid gases Atomic Bose-Einstein condensate (sodium) Molecular Bose-Einstein condensate (lithium 6Li2) Pairs of fermionic atoms (lithium-6)