title “when freezing cold is not cold enough - new forms of matter close to absolute zero...

“When freezing cold is not cold enough - new forms of matter close

to absolute zero temperature”Wolfgang Ketterle

Massachusetts Institute of TechnologyMIT-Harvard Center for Ultracold Atoms

9/2/09Meridian Lecture

Space Telescope Science InstituteBaltimore

Quantum Gases

The coldest matterin the universe

What is temperature?

A measure of energy

One form of energy is motion(kinetic energy).

Cold particles move slowly

Hot particlesare fast

What is the lowest temperatures possible?

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 differencein temperature between

summer and winter?

20 %

How cold is interstellar space?

3 K

How cold is itin our laboratories?

Nanokelvin:A billion times

colder than interstellarspace

Why can you makenew discoveries

at cold temperatures?

What happens to atomsat low temperatures?

They slow down600 mph (300 m/sec) 1 cm/sec

They march in lockstep

Matter made of waves!

Energy

Pop

ulat

ion

per

ener

gy s

tate

What is Bose Einstein Condensation?

T=Tc

Bose-Einstein distribution

Energy

Pop

ulat

ion

per

ener

gy s

tate

What is Bose Einstein Condensation?

Bose-Einstein distribution

T<Tc

Condensate!

Energy

Pop

ulat

ion

per

ener

gy s

tate

What is Bose Einstein Condensation?

Bose-Einstein distribution

T<Tc

Condensate!

Laser lightOrdinary light

Photons/atoms moving randomly Photons/atoms are one big wave

* 1925

)(n1

1)( TkBe

1

1

TkBe

Max Planck

Black-Body Radiation“Photons”

Gases (Atoms and Molecules)

The cooling methods

• Laser cooling• Evaporative cooling

Hot atoms

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 …

2.5 cm

Laser cooling

Evaporative cooling

Phillips et al. (1985)Pritchard et al. (1987)

One challenge …

experimental complexity

Sodium laser cooling experiment (1992)

Sodium BEC I experiment (2001)

Dan Kleppner Tom Greytak Dave Pritchard

Dan Kleppner

Dave Pritchard

Eric Cornell Carl WiemanWolfgang Ketterle

Bill PhillipsPhD

PhD

Postdoc

Under-graduate

PhD

RandyHulet

PhD

Norman Ramsey

PhD

I.I. Rabi

PhD

Postdoc

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

How do we show that the Bose-Einstein

condensate has very low energy?

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

How to measure temperature?

Kinetic energy mv2/2 = kBT/2

Gas Effusive atomic beam

How to measure temperature?

Kinetic energy mv2/2 = kBT/2

Gas Effusive atomic beam

CCD

CCD

Ballistic expansion: direct information about velocity distribution

CCD

Absorption image: shadow of atoms

Ballistic expansion: direct information about velocity distribution

The shadow of a cloud of bosonsas the temperature is decreased

(Ballistic expansion for a fixed time-of-flight)

Temperature is linearly related to the rf frequency which controls the evaporation

Distribution of the times when data images were takenduring 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

How can you prove that atoms march in lockstep?

Atoms are one single waveAtoms are coherent

One paint ball on a white wallTwo

Paint does not show wave properties

One laser beam on a white wall

Light shows wave properties

One laser beam on a white wallTwo

Fringe pattern:Bright-dark-bright-dark

Light shows wave properties

Two condensates ...

50 m

Interference of two Bose-Einstein condensates

Andrews, Townsend, Miesner, Durfee, Kurn, Ketterle, Science 275, 589 (1997)

How do we show that the gas is superfluid?

Rigid body:

Vortices in nature

Spinning a Bose-Einstein condensate

Rotatinggreen laser beams

The rotating bucket experiment with a superfluid gas 100,000 thinner than air

Two-component vortex Boulder, 1999Single-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 chipswith optical tweezers

BECproductionBEC

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, 020401 (2002).

Atom chip with waveguides

Splitting of condensates

15ms Expansion

Two condensates

1mm

One trappedcondensate

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, 021604(R) (2005).

Two condensates

Splitting of condensates

The goal:Atom interferometry:Matter wave sensors

Use ultracold atoms to sense

Rotation NavigationGravitation Geological exploration

Cold moleculesCold fermions

Current Research

Can electrons form a Bose-Einstein condensateand 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 condensateand 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 aboutsuperconductivity

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, 250401 (2003)

BEC of Fermion Pairs (“Molecules”)

Boulder Nov ‘03Innsbruck Nov ‘03, Jan ’04MIT Nov ’03Paris March ’04Rice, Duke

These days: Up to 10 million condensed molecules

Atomic Bose-Einsteincondensate (sodium)

Molecular Bose-Einsteincondensate (lithium 6Li2)

Pairs of fermionicatoms (lithium-6)

Gallery of superfluid gases

Ultracold atomsA “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 atomsA “toolbox” for designer matter

Need 100 million times colder temperatures