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

What is energy Quantum Gases The coldest matter in the universe

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=mc 2 ) that they from a black hole – at the Planck temperature of K)

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

How cold is interstellar space? 3 K

Nanokelvin temperatures How cold is it in our laboratories? Nanokelvin: A billion times colder than interstellar space

Nanokelvin temperatures Why can you make new discoveries at cold temperatures?

Nobel medal

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

Why do photons not Bose condense Energy Population per energy state What is Bose Einstein Condensation? T=T c Bose-Einstein distribution

Why do photons not Bose condense Energy Population per energy state What is Bose Einstein Condensation? Bose-Einstein distribution T<T c Condensate!

Why do photons not Bose condense Energy Population per energy state What is Bose Einstein Condensation? Bose-Einstein distribution T<T c Condensate!

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

Bose/Einstein * 1925

BE statistics and black body law Max Planck Black-Body Radiation “Photons” Gases (Atoms and Molecules)

The concepts The cooling methods Laser cooling Evaporative cooling

Hot atoms

Laser beams

Hot atoms Laser beams Fluorescence

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

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

MOT 2.5 cm Laser cooling

The concepts Evaporative cooling

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

Guinness Book Record

The real challenge One challenge … experimental complexity

WK and Dark SPOT Sodium laser cooling experiment (1992)

Sodium BEC I experiment (2001)

Evaporative cooling Dan KleppnerTom Greytak Dave Pritchard

Family tree Dan Kleppner Dave Pritchard Eric CornellCarl WiemanWolfgang Ketterle Bill Phillips PhD Postdoc Under- graduate PhD Randy Hulet PhD Norman Ramsey PhD I.I. Rabi PhD Postdoc

Key factors for success: Funding Technical infrastructure Excellent collaborators Tradition and mentors

Probing BEC How do we show that the Bose-Einstein condensate has very low energy?

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

Effusive beam How to measure temperature? Kinetic energy mv 2 /2 = k B T/2

Effusive beam How to measure temperature? Kinetic energy mv 2 /2 = k B T/2

CCD

Ballistic expansion:direct information about velocity distribution

CCD Absorption image: shadow of atoms Ballistic expansion:direct information about velocity distribution

BEC B&W AVI The shadow of a cloud of bosons as the temperature is decreased (Ballistic expansion for a fixed time-of-flight) Temperature is linearly related to the rf frequency which controls the evaporation

Hour distribution Distribution of the times when data images were taken during one year between 2/98-1/99

Key factors for success: Some funding Technical infrastructure Excellent collaborators Tradition and mentors

Key factors for success: Some funding Technical infrastructure Excellent collaborators Tradition and mentors Physical endurance

Molecule of the year How can you prove that atoms march in lockstep? Atoms are one single wave Atoms are coherent

One paint ball on a white wall Two Paint does not show wave properties

One laser beam on a white wall Light shows wave properties

One laser beam on a white wall Two Fringe pattern: Bright-dark-bright-dark Light shows wave properties

Water waves

Two condensates... Cutting condensates

Interference of two Bose-Einstein condensates Interference pattern Andrews, Townsend, Miesner, Durfee, Kurn, Ketterle, Science 275, 589 (1997)

Nobel Diploma

How do we show that the gas is superfluid?

Rotating buckets

Velocity profile Rigid body:

Vortex structure

Vortices in Nature Vortices in nature

Toilet 1

Toilet

Spinning a Bose-Einstein condensate Rotating green laser beams The rotating bucket experiment with a superfluid gas 100,000 thinner than air Two-component vortex Boulder, 1999 Single-component vortices Paris, 1999 Boulder, 2000 MIT 2001 Oxford 2001 J. Abo-Shaeer, C. Raman, J.M. Vogels, W.Ketterle, Science, 4/20/2001

BEC on a microchip Current Research

Loading sodium BECs into atom chips with optical tweezers BEC production BEC arrival 44 cm T.L.Gustavson, A.P.Chikkatur, A.E.Leanhardt, A.Görlitz, S.Gupta, D.E.Pritchard, W. Ketterle, Phys. Rev. Lett. 88, (2002). Atom chip with waveguides

Splitting of condensates 15ms Expansion Two condensates 1mm One trapped condensate

Trapped 15ms expansion 1mm Two condensates Splitting of condensates

Two condensates Splitting of condensates Y. Shin, C. Sanner, G.-B. Jo, T. A. Pasquini, M. Saba, W. Ketterle, D. E. Pritchard, M. Vengalattore, and M. Prentiss: Phys. Rev. A 72, (R) (2005).

Two condensates Splitting of condensates The goal: Atom interferometry: Matter wave sensors Use ultracold atoms to sense Rotation  Navigation Gravitation  Geological exploration

Cold molecules Cold fermions Current Research

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

M.W. Zwierlein, C. A. Stan, C. H. Schunck, S.M. F. Raupach, S. Gupta, Z. Hadzibabic, W.K., Phys. Rev. Lett. 91, (2003) BEC of Fermion Pairs (“Molecules”) Boulder Nov ‘03 Innsbruck Nov ‘03, Jan ’04 MIT Nov ’03 Paris March ’04 Rice, Duke These days: Up to 10 million condensed molecules

Atomic Bose-Einstein condensate (sodium) Molecular Bose-Einstein condensate (lithium 6 Li 2 ) Pairs of fermionic atoms (lithium-6) Gallery of superfluid gases

Ultracold atoms A “toolbox” for designer matter Normal matter Tightly packed atoms Complicated Interactions Impurities and defects

Matter of ultracold atoms 100 million times lower density Interactions understood and controlled no impurities exact calculations possible Ultracold atoms A “toolbox” for designer matter Need 100 million times colder temperatures