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Wolfgang Ketterle,
Nobel Prize Laureate in Physics 2001, Professor
at MIT
Kälter als kalt:
Forschung am absoluten
Nullpunkt
Tiefe Temperaturen –
ein Rezept für Entdeckungen
Kelvin-Physik
Flüssiges Helium, Supraleitung
Milli-Kelvin-Physik
Supraflüssiges Helium-3
Micro-Kelvin-Physik
Laserkühlen, Speichern von Atomen
Nano-Kelvin-Physik
Bose-Einstein-Kondensation
Phase transitions: properties of matter change
dramatically when cooled below a specific temperature
Water/Ice: 0 degrees Celsius, 273 Kelvin
Liquid oxygen -183°C
Liquid nitrogen -196°C
Phase transitions from liquid to solid
Water freezes at 0°C
Domestic freezer: -20°C
Whisky: 80 Proof (vol. 40) freezing point of -26°C
Dry Ice: -78°C
Pure alcohol
Methanol (-98°C), Ethanol (-114°C), Isopropanol (-89°C)
Wolfgang Ketterle - Kälter als kalt: Forschung am absoluten Nullpunkt
4 Kelvin: helium gas becomes liquid
2.8 Kelvin: temperature of interstellar space
(cosmic microwave background)
100 times colder than room temperature
Millikelvin
Microkelvin
Nanokelvin: 10-9 Kelvin
100 billion times colder than room temperature
Die kälteste Materie
im Universum
Nanokelvin Atome
und ein besonderer Phasenübergang:
Bose-Einstein-Kondensation
Was machen Atome bei
tiefen Temperaturen?
Sie werden langsamer
1000 km/h (300 m/s) 1 mm/s
pressure =
density times kinetic energy
Lower temperature leads to lower pressure
Demo
Was machen Atome bei
tiefen Temperaturen?
Sie werden langsamer
1000 km/h (300 m/s) 1 mm/s
Sie marschieren
im Gleichschritt
Molecule of the year
Das Bose-Einstein Kondensat:
Materie aus Materiewellen!
Molecule of the year
Das Bose-Einstein Kondensat:
Materie aus Materiewellen!
Photonen / Atome bewegen sich in alle
Richtungen
Photonen / Atome sind eine einzige
Welle
LaserlichtNormales Licht
Kühlmethoden
• Laserkühlung
• Verdampfungskühlung
•Atomfallen
• Magnetische Fallen
• Optische Fallen
Wie bekommt man sehr
kalte Atomwolken?
Wolfgang Ketterle - Kälter als kalt: Forschung am absoluten Nullpunkt
Wolfgang Ketterle - Kälter als kalt: Forschung am absoluten Nullpunkt
Wolfgang Ketterle - Kälter als kalt: Forschung am absoluten Nullpunkt
2.5 cm
Laser cooling
Ultrahoch-Vakuum-Kammer –
der weltbeste Thermos-Behälter
Kasten aus
elektrischen
und/oder
magnetischen
Feldern
Eine Million Nanokelvin Atome
CCD
Ultrahoch-Vakuum-Kammer
mm
Wie mißt man Temperatur?
Kinetische Energie mv2/2 = kBT/2
v=Radius/Flugzeit
Der Schatten einer Atomwolke
für immer tiefere Temperaturen
(Ballistische Expansion mit einer vorgegebenen Flugzeit)
Temperatur hängt linear von der Radiofrequenz ab,
die die Verdampfung steuert
Der Schatten einer Atomwolke
für immer tiefere Temperaturen
(Ballistische Expansion mit einer vorgegebenen Flugzeit)
Temperatur hängt linear von der Radiofrequenz ab,
die die Verdampfung steuert
Wie weist man nach, daß alle Atome im Gleichschritt marschieren?
Atome sind eine Welle
Atome sind kohärent
Ein Farbbeutel auf einer weißen Wand
Zwei
Farbe zeigt keine Welleneigenschaften
Ein Laserstrahl auf einer weißen Wand
Licht zeigt Welleneigenschaften
Ein Laserstrahl auf einer weißen Wand
Zwei
Licht zeigt Welleneigenschaften
Streifenmuster:
hell - dunkel - hell - dunkel
Two condensates ...
50 m
Interferenz von zwei Bose-Einstein-Kondensaten
Andrews, Townsend, Miesner, Durfee, Kurn, Ketterle, Science 275, 589 (1997)
rel
dB
mv
h

TOF
rel
t
d
v 
Interferenz von Atomen
Materie-Wellen-Interferenz
… als Präzisionsmessung: Atom-Interferometrie
Messung von Beschleunigungen
• g: Erdbeschleunigung
• G: Gravitations-Konstante
• Photonen-Rückstoß: Bestimmung der
Feinstruktur-Konstante 
• Navigation ohne GPS
Superconductivity = electrons march in lockstep
This can create a current which flows without dissipation
(no power supply, no battery)
This current creates a magnetic field
Demonstration:
eddy currents– currents in copper which create a
magnetic field
Demo
Demonstration:
eddy currents– currents in copper which create a
magnetic field
Superconductor
Demonstration:
a piece of (copper oxide) ceramic is cooled down
there is a phase transition
at the phase transition, electrons can march in lockstep
(they pair up and form a macroscopic quantum state)
this superconducting current has no dissipation
(no electrical resistance) and is therefore persistent
it creates a magnetic field, and the magnet floats
Demo
This can be explained by Faraday’s law of induction
and dissipationless currents.
But there is more!
Now: cool down
This can be explained by Faraday’s law of induction
and dissipationless currents.
But there is more!
At the phase transition, the superconducting material becomes
an extreme diamagnetic material, which expels all magnetic
fields by generating the opposite magnetic field
Meissner effect
But there is more! Demo
Meissner effect
Meissner effect Flux penetration and pinning
Type II superconductors at
high magnetic fields
Type I superconductors
Type II superconductors at
low magnetic fields
“Our” superconductor:
Yttrium barium copper oxide (YBCO), type II superconductor
Tc around 90 K (-183°C)
So far:
Polycrystalline form with small grains
Low critical current. Meissner effect dominates over flux pinning.
(However, due to saturated current, flux is not completely
expelled).
Now:
Single domain (single crystal): high critical current.
Flux penetration
Flux pinning enhanced with impurities (e.g. silver).
Demo
Flux pinning and hysteresis
Flux pinning provides lateral forces
Forces are attractive and repulsive:
Magnetic suspension effect
Magnetic bearing
We have seen:
Persistent currents
Phase transition to diamagnetic material (Meissner effect)
Moderne Materialien verändern die Welt
Ein neues Material!
• Sehr kalt
• Materie aus Wellen
• Superfluid
Unser Zugang: Atomare Legos
Kühle Atome bis nahe zum absoluten Nullpunkt:
Nanokelvin, bring sie zum Stillstand
Füge sie zusammen, so daß sie sich
wie wichtige Materialien verhalten
Untersuchung von Materialien auf einem
grundlegenden Niveau
Quanten-Simulator:
ein Quantenrechner für spezielle Zwecke
Ultrahoch-Vakuum-Kammer –
der weltbeste Thermos-Behälter
Kasten aus
elektrischen
und/oder
magnetischen
Feldern
Eine Million Nanokelvin Atome
Laserstrahlen
Radiofrequenz- und
Mikrowellen
Eine Million Nanokelvin Atome
Kasten aus
elektrischen
und/oder
magnetischen
Feldern
Ultrahoch-Vakuum-Kammer
Quartz crystal
Kochsalz
NaCl
Wie realisiert man periodische Potentiale für Atome?
(Gitterphysik, Isolator, Metall, Bandstruktur etc.)
Zwei Laser-Strahlen bilden eine Stehwelle
Wolfgang Ketterle - Kälter als kalt: Forschung am absoluten Nullpunkt
Drei-dimensionales optisches Gitter
Greiner labs, Harvard
Tunneling: Atoms go through the “walls” of the egg carton
Tunneling: Atoms go through the “walls” of the egg carton
Atoms tunnel coherently – they behave as one quantum wave
MPQ, Garching
Quantenphasenübergang
von einer Supraflüssigkeit
zu einem Isolator
Suprasolidität –
eine neue Form der Materie
… es ist ein Gas, eine Flüssigkeit,
ein Festkörper ...
… alles gleichzeitig ...
Wolfgang Ketterle - Kälter als kalt: Forschung am absoluten Nullpunkt
Untersuchung von Materialeigenschaften an einem
Modell, das 1000x vergrößert ist
(Atomabstand is Mikrometer anstelle Nanometer)
Probiere (und verstehe) welche Materialien und
Phänomene in der Natur möglich sind!
Nutze Quantenmechanik für neue Anwendungen
Quantentechnologien
Auf der Suche nach neuen Materialien
Wolfgang Ketterle - Kälter als kalt: Forschung am absoluten Nullpunkt
J. Appl. Phys. 63, 447 (1987)
Much smaller hysteresis for samples with small grains
Ampere’s law for parallel magnetic fields: surface current
sheet causes difference between external and internal B
field
Max delta-B: critical current density times
grain size (assuming saturation in currents)

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Wolfgang Ketterle - Kälter als kalt: Forschung am absoluten Nullpunkt