When freezing cold is not cold enough new
- Slides: 83
“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
Quantum Gases The coldest matter in the universe
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?
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 1032 K)
What is the difference in temperature between summer and winter? 20 %
How cold is interstellar space? 3 K
How cold is it in our laboratories? Nanokelvin: A billion times colder than interstellar space
Why can you make new discoveries at cold temperatures?
What happens to atoms at low temperatures? They slow down 600 mph (300 m/sec) 1 cm/sec They march in lockstep
Matter made of waves!
Population per energy state What is Bose Einstein Condensation? Bose-Einstein distribution T=Tc Energy
Population per energy state What is Bose Einstein Condensation? T<Tc Condensate! Bose-Einstein distribution Energy
Population per energy state What is Bose Einstein Condensation? T<Tc Condensate! Bose-Einstein distribution Energy
Ordinary light Photons/atoms moving randomly Laser light Photons/atoms are one big wave
* 1925
Gases (Atoms and Molecules) Black-Body Radiation “Photons” Max Planck
The cooling methods • Laser cooling • Evaporative cooling
Hot atoms
Hot atoms Laser beams
Hot atoms Fluorescence Laser beams
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 …
Laser cooling 2. 5 cm
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
I. I. Rabi Ph. D Norman Ramsey Ph. D Dan Kleppner Ph. D Dave Pritchard Postdoc Bill Phillips Ph. D Eric Cornell Undergraduate Postdoc Wolfgang Ketterle Randy Hulet Carl Wieman
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? Gas Effusive atomic beam Kinetic energy mv 2/2 = k. BT/2
How to measure temperature? Gas Effusive atomic beam Kinetic energy mv 2/2 = k. BT/2
CCD
CCD Ballistic expansion: direct information about velocity distribution
CCD Ballistic expansion: direct information about velocity distribution Absorption image: shadow of atoms
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
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
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
Two condensates. . .
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 The rotating bucket experiment with a superfluid gas 100, 000 thinner than air Rotating green laser beams 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
Current Research BEC on a microchip
Loading sodium BECs into atom chips with optical tweezers 44 cm BEC arrival BEC production 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 1 mm One trapped 15 ms condensate Expansion Two condensates
Splitting of condensates 1 mm Trapped 15 ms 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: The goal: Matter wave sensors Use ultracold atoms to sense Rotation Navigation Gravitation Geological exploration
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
BEC of Fermion Pairs (“Molecules”) These days: Up to 10 million condensed molecules Boulder Innsbruck MIT Paris Rice, Duke Nov ‘ 03, Jan ’ 04 Nov ’ 03 March ’ 04 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-Einstein condensate (sodium) Molecular Bose-Einstein condensate (lithium 6 Li 2) Pairs of fermionic atoms (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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- Expansion upon freezing
- Expansion upon freezing
- Phase changes
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- Air freezing point
- Freezing of fish
- Plate freezing technology
- Iqf tunnel freezer
- Preservation by freezing
- Indirect contact freezing
- What is vapor pressure lowering
- Why freezing point decreases on adding solute
- Pure solvent
- Expansion upon freezing
- Condensation particles
- Condensation evaporation melting freezing
- Cool treeless and dry
- Expansion upon freezing
- δ+
- Upper air soundings
- Fahrenheit brine
- Dehydrofreezing
- Transmission/timeout freezing
- Freezing point of xylene
- Calculate molar mass from freezing point
- Aimlab freezing
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- Freezing of fish
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- Kinetic particle theory of matter
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