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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.

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Title
Title

“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 Institute

Baltimore


What is energy
What is energy

Quantum Gases

The coldest matterin the universe


What is temperature
What is temperature

What is temperature?

A measure of energy

One form of energy is motion(kinetic energy).


Cold particles move slowly

Hot particlesare fast



What is temperature1
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 temperature2
What is temperature

What is the differencein temperature betweensummer and winter?

20 %


How cold is interstellar space?

3 K


Nanokelvin temperatures
Nanokelvin temperatures

How cold is itin our laboratories?

Nanokelvin:A billion timescolder than interstellar

space


Nanokelvin temperatures1
Nanokelvin temperatures

Why can you makenew discoveriesat cold temperatures?



Atom slow down
Atom slow down

They slow down

600 mph (300 m/sec)

1 cm/sec

What happens to atomsat low temperatures?

They march in lockstep


Molecule of the year
Molecule of the year

Matter made of waves!



Why do photons not bose condense
Why do photons not Bose condense

What is Bose Einstein Condensation?

Population per energy state

Bose-Einstein distribution

T=Tc

Energy


Why do photons not bose condense1
Why do photons not Bose condense

T<Tc

Condensate!

What is Bose Einstein Condensation?

Population per energy state

Bose-Einstein distribution

Energy


Why do photons not bose condense2
Why do photons not Bose condense

What is Bose Einstein Condensation?

T<Tc

Condensate!

Population per energy state

Bose-Einstein distribution

Energy


Laser beam and light bulb
Laser beam and light bulb

Photons/atoms are one big wave

Photons/atoms moving randomly

Ordinary light

Laser light



Be statistics and black body law
BE statistics and black body law

Gases (Atoms and Molecules)

Black-Body Radiation

“Photons”

Max Planck


The concepts
The concepts

The cooling methods

  • Laser cooling

  • Evaporative cooling



Laser beams

Hot atoms


Fluorescence

Laser beams

Hot atoms


Laser beams

Fluorescence

If the emitted radiation is blue shifted

(e.g. by the Doppler effect) ….


Laser beams

Cold atoms: 10 – 100 K

Fluorescence

Chu, Cohen-Tannoudji, Phillips, Pritchard, Ashkin, Lethokov, Hänsch, Schawlow, Wineland …


MOT

Laser cooling

2.5 cm


The concepts1
The concepts

Evaporative cooling


Magnetic trap setup gif
Magnetic trap setup (GIF)

Phillips et al. (1985)

Pritchard et al. (1987)



The real challenge
The real challenge

One challenge …

experimental complexity


Wk and dark spot
WK and Dark SPOT

Sodium laser cooling experiment (1992)



Evaporative cooling
Evaporative cooling

Dave Pritchard

Dan Kleppner

Tom Greytak


Family tree
Family tree

I.I. Rabi

PhD

Norman Ramsey

PhD

Dan Kleppner

PhD

PhD

PhD

Under-

graduate

Dave Pritchard

Postdoc

RandyHulet

Bill Phillips

Postdoc

PhD

Eric Cornell

Wolfgang Ketterle

Carl Wieman



Probing bec
Probing BEC

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


Magnetic trap setup
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
Effusive beam

Effusive atomic beam

Gas

How to measure temperature?

Kinetic energy mv2/2 = kBT/2


Effusive beam1
Effusive beam

Effusive atomic beam

Gas

How to measure temperature?

Kinetic energy mv2/2 = kBT/2



CCD

Ballistic expansion: direct information about velocity distribution


Absorption image: shadow of atoms

CCD

Ballistic expansion: direct information about velocity distribution


Bec b w avi
BEC B&W AVI

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


Hour distribution
Hour distribution

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

  • Physical endurance


Molecule of the year2
Molecule of the year

How can you prove that atoms march in lockstep?

Atoms are one single waveAtoms are coherent


Two

One paint ball on a white wall

Paint does not show wave properties


One laser beam on a white wall

Light shows wave properties


Two

One laser beam on a white wall

Fringe pattern:

Bright-dark-bright-dark

Light shows wave properties



Cutting condensates
Cutting condensates

Two condensates ...


Interference pattern
Interference pattern

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?



Velocity profile
Velocity profile

Rigid body:




Vortices in nature
Vortices in Nature

Vortices in nature




Spinning a Bose-Einstein condensate

The rotating bucket experiment with a superfluid gas

100,000 thinner than air

Rotating

green laser beams

Two-component vortexBoulder, 1999Single-component vorticesParis, 1999 Boulder, 2000 MIT 2001 Oxford 2001

J. Abo-Shaeer, C. Raman, J.M. Vogels,

W.Ketterle, Science, 4/20/2001


Current Research

BEC on a microchip


Loading sodium BECs into atom chipswith optical tweezers

44 cm

Atom chip with waveguides

BECproduction

BECarrival

T.L.Gustavson, A.P.Chikkatur, A.E.Leanhardt, A.Görlitz, S.Gupta, D.E.Pritchard, W. Ketterle, Phys. Rev. Lett. 88, 020401 (2002).


Splitting of condensates

1mm

One trappedcondensate

15ms

Expansion

Two condensates


Splitting of condensates

1mm

Trapped

15ms

expansion

Two condensates


Splitting of condensates

Two 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).


Splitting of condensates

Two condensates

Atom interferometry:

Matter wave sensors

The goal:

Use ultracold atoms to sense

Rotation  Navigation

Gravitation  Geological exploration


Current Research

Cold molecules

Cold fermions


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 aboutsuperconductivityof electrons from cold atoms?

Yes, by studying pairing and superfluidity of atoms with an odd number of protons, electrons and neutrons


BEC of Fermion Pairs (“Molecules”)

These days: Up to 10 million condensed molecules

Boulder Nov ‘03Innsbruck Nov ‘03, Jan ’04

MIT Nov ’03Paris March ’04

Rice, Duke

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)


Gallery of superfluid gases

Atomic Bose-Einsteincondensate (sodium)

Molecular Bose-Einsteincondensate (lithium 6Li2)

Pairs of fermionicatoms (lithium-6)


Ultracold atoms

A “toolbox” for designer matter

  • Normal matter

  • Tightly packed atoms

  • Complicated Interactions

  • Impurities and defects


Ultracold atoms

A “toolbox” for designer matter

  • Matter of ultracold atoms

  • 100 million times lower density

  • Interactions understood and controlled

  • no impurities

  • exact calculations possible

Need 100 million times colder temperatures


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