Introduction of bose einstein condensation
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Transcript of Introduction of bose einstein condensation
New State of Matter Revealed: Bose-Einstein Condensation
The Noble Prize in Physics 2001
by Zheng Zhao
Suranaree University of TechnologyM5810024
The Nobel Prize in Physics for 2001 was awarded jointly to:
—-“for the achievement of Bose-Einstein condensation in dilute gases of alkali atoms, and for early fundamental studies of the properties of the condensates.”
Eric CornellPrize share 1/3
Wolfgang KetterlePrize share 1/3
Carl WiemanPrize share 1/3
Source: https://www.nobelprize.org/nobel_prizes/physics/laureates/2001/
Biography [Wolfgang Ketterle]
Outline
Introduction of Bose-Einstein Condensation
BEC achieving in MIT
Summary
In 1957, born in Heidelberg, Germany. In 1976, University of Heidelberg In 1982, M.S Technical University in Munich In 1986, Ph.D Max Planck Institute
Wolfgang KetterlePrize share 1/3
In 1990, joined the group of David E. Pritchard in the Research Laboratory of Electronics at MIT (RLE)
In 1995, achieving BEC in sodium
Biography [Wolfgang Ketterle]
Introduction of Bose-Einstein Condensation
Biography [Wolfgang Ketterle]
Outline
BEC achieving in MIT
Summary
Introduction of Bose-Einstein Condensation
De Broglie (1929 Nobel Prize winner) proposed that all matter is composed of waves. Their wavelength are given by,
Q1: What is the Bose-Einstein Condensation
λ = hmv
= de Broglie wavelength h = Planck’s constant m = mass v = velocity
λ
Thermal De Broglie wavelength was given by,
λ = h2πmkBT
Introduction of Bose-Einstein CondensationQ1: What is the Bose-Einstein Condensation
= de Broglie wavelength h = Planck’s constant m = mass = Boltzmann constant T = temperaturekB
λ
Introduction of Bose-Einstein CondensationQ1: What is the Bose-Einstein Condensation
classical gas: T>>Tc “billiard balls”
T>Tc, λdB = h/mv ∝T1/2
“wave packets”T=Tcrit, λdB = d“Mater wave overlap”
, BECT=0, Pure Bose condensate “Giant matter wave”
Source: https://www.youtube.com/watch?v=shdLjIkRaS8
Introduction of Bose-Einstein CondensationQ1:What is Bose-Einstein Condensation (BEC)?
In brief, creating a BEC is thus simple in principle:
“make a gas extremely cold until the atomic wave packets start to overlap.”
But, It takes 70 years to accomplish =
BEC achieving in MIT
Biography [Wolfgang Ketterle]
Outline
Introduction of Bose-Einstein Condensation
Summary
BEC achieving in MIT
Q2: How is BEC made?
• Laser Cooling — precool the gas atoms
• Magneto-optical Trap (MOT) — trap gas atoms
• Evaporative Cooling — second cooling stage
The Nobel Prize in Physics for 1997 was awarded jointly to:
—-“for development of method to cool and trap atoms with laser light.”
Steven Chu Claude Cohen-Tannoudji William D.PhillipsPrize share 1/3 Prize share 1/3 Prize share 1/3
• Laser Cooling — precool the gas atoms
BEC achieving in MIT Q2: How is BEC made?
Source: https://www.nobelprize.org/nobel_prizes/physics/laureates/1997/
BEC achieving in MIT
• Photons — particles carrying momenta like Ping-Pong Balls
• Slowing the motion of an atom —- bouncing laser light off the atomsPhotons
“ping-pong Balls”an atom
“bowling ball”
1. “Bowling ball” and “Ping-Pong balls”
• Laser Cooling — precool the gas atomsQ2: How is BEC made?
BEC achieving in MIT
2. Tuning the laser
• Only laser light with the correct color (frequency) can be absorbed by the atoms
• If the color is wrong, the atoms cannot absorb the photons
• Doppler Effect — avoid accelerating the atoms (blast off atoms)
• Laser Cooling — precool the gas atomsQ2: How is BEC made?
BEC achieving in MIT
• right color laser — photons to be absorbed by an approaching atom — the atom will be slowed down.
• wrong color laser — photons can not be be absorbed by the receding atom — Doppler effect.
1. laser trapping
approaching atom slow down
receding atom do not change
Q2: How is BEC made?
• Magneto-optical Trap (MOT) — trap gas atoms
• lasers are sent in from all the different directions, the atoms can get cold very quickly.
1. laser trapping
BEC achieving in MIT Q2: How is BEC made?
• Magneto-optical Trap (MOT) — trap gas atoms
• Problem: 1. Laser cooling — atoms — 1/10000K— This is still too hot for BEC.
• Solution: Evaporative cooling
BEC achieving in MIT
thermos bottle
2. Magnetic trapping
Q2: How is BEC made?
• Magneto-optical Trap (MOT) — trap gas atoms
=
• The atoms — tiny compasses (or magnet) — can be pulled by magnetic fields.
• A magnetic field — push the atoms inwards — magnetic trap.
• http://www.colorado.edu/physics/2000/bec/mag_trap.html
BEC achieving in MIT
2. Magnetic trapping
Q2: How is BEC made?
• Magneto-optical Trap (MOT) — trap gas atoms
BEC achieving in MIT
thermos bottle
2. Magnetic trapping
Magneto-optical Trap (MOT)
=
Q2: How is BEC made?
• Magneto-optical Trap (MOT) — trap gas atoms
BEC achieving in MIT
• Evaporation takes heat.
• eg. A cup of coffee — steam escapes — faster atoms escape — leaving slower ones
• http://www.colorado.edu/physics/2000/bec/evap_cool.html
• Evaporative Cooling — second cooling stageQ2: How is BEC made?
BEC achieving in MIT
Biography [Wolfgang Ketterle]
Outline
Introduction of Bose-Einstein Condensation
Summary
Time-of-flight absorption images of BEC with sodium in MIT
BEC achieving in MIT
Source: (http://cua.mit.edu/ketterle_group/animations.htm)
Observation of BEC with sodium by Time of flight absorption images (MIT)
BEC achieving in MIT
Source: (http://cua.mit.edu/ketterle_group/animations.htm)
BEC achieving in MIT
Observation of Bose-Einstein condensation by absorption images. Shown — absorption vs. two spatial dimensions. left: above the transition point; middle: just after the condensate appeared; right: after further evaporative cooling — left an almost pure condensate.
Source: (http://cua.mit.edu/ketterle_group/animations.htm)
Biography [Wolfgang Ketterle]
Outline
Introduction of Bose-Einstein Condensation
BEC achieving in MIT
Summary
Summary
• BEC shares the same "specialness" with laser light.
• Outlook: When atoms behave as wave
• The fifth state of matter — BEC.
Summary
(http://cua.mit.edu/ketterle_group/animations.htm)
• atom optics (studying the optical properties of atoms)
• precision atomic clocks
• other measurements of fundamental standards
• communications and computation.
• Fundamental understanding of quantum mechanics.
• This is a completely new area. Applications are too early to predict. The atom laser can be used in:
• Outlook: When atoms behave as wave
• W. Ketterle, When Atoms Behave as Wave: Bose-Einstein Condensation and The Atom Laser, Nobel lecture, Dec 2001
• D. E. Pritchard, Bose-Einstein Condensation: A Double Pot of Gold. (http://web.mit.edu/physics/news/physicsatmit/physicsatmit_02_bec.pdf)
• Homepage of the Nobel e-Museum. (https://www.nobelprize.org/nobel_prizes/physics/laureates/2001/)
• BEC Homepage at the University of Colorado. (http://www.colorado.edu/physics/2000/bec/index.html)
• Ketterle Group Homepage. (http://www.cua.mit/ketterle_group/).
Reference
Thank you for your attention
Welcome questions
BEC achieving in MIT
• Using the Doppler Effect to avoid accelerating the atoms (blast off atoms)
• Laser Cooling — precool the gas atomsQ2: How is BEC made?
3. Using the Doppler Effect
approaching
chasing
BEC achieving in MIT
3. Using the Doppler Effect
• The atom — receding from the laser source — the wavelength — longer — redshift
• The atom — approaching the laser source — the wavelength — shorter — blueshift
• The electron — do not absorb redshift photon — the photon will go through the atom
• Laser Cooling — precool the gas atomsQ2: How is BEC made?