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Title. “New forms of quantum matter near absolute zero temperature” Wolfgang Ketterle Massachusetts Institute of Technology MIT-Harvard Center for Ultracold Atoms 5/23/06 NASA workshop Airlie Center. Title. The ongoing revolution in atomic physics …. Title.

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**Title**“New forms of quantum matter near absolute zero temperature” Wolfgang Ketterle Massachusetts Institute of TechnologyMIT-Harvard Center for Ultracold Atoms 5/23/06 NASA workshop Airlie Center**Title**The ongoing revolution in atomic physics …**Title**Enabling technology:Nanokelvin temperatures**The concepts**The cooling methods • Laser cooling • Evaporative cooling**Height of atmosphere**e-(106) 300 mK h=1 cm Potential (gravitational) energy mgh = kBT/2 (g: gravitational acceleration) How to measure temperature Height of the atmosphere 1 nK h= 30 nm 300 K h=10 km In thermal equilibrium: Potential energy ~ kinetic energy**Lowest temperature ever achieved: 450 picokelvin**1.05 nK 1 cm 780 pK Trapping a sodium BECwith a single coil 450 pK A.E. Leanhardt, T.A. Pasquini, M. Saba, A. Schirotzek, Y. Shin, D. Kielpinski, D.E. Pritchard, and W. Ketterle, Science 301, 1513 (2003). Temperature measurement by imaging the size of the trapped cloud**Precision measurements**Precision measurements with Bose-Einstein condensates ... We have to get rid of perturbing fields … • Gravity • Magnetic fields**What distinguishes nanokelvin?**• Physics • BEC Phase transition Quantum reflection • Interactions • Ease of Manipulation**BEC at JILA and MIT**BEC @ JILA, June ‘95(Rubidium) BEC @ MIT, Sept. ‘95 (Sodium)**Quantum Reflection of Ultracold Atoms**T.A. Pasquini, Y. Shin, C. Sanner, M. Saba, A. Schirotzek, D.E. Pritchard, W.K. • Phys. Rev. Lett. 93, 223201 (2004) • Preprint (2006)**Sodium BEC**Silicon surface**Quantum Reflection from Nanopillars**Solid Si surface Reduced density Si surface Reflection Probability Velocity (mm/s) 1 mm/s is 1.5 nK x kB kinetic energy**What distinguishes nanokelvin?**• Physics • BEC Phase transition Quantum reflection • Interactions • Ease of Manipulation**Moving condensates**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 Very recent progress: 200 ms coherence time for an atom chip interferometer 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**What distinguishes nanokelvin?**• Physics • BEC Phase transition Quantum reflection • Interactions • Ease of Manipulation**Two of the biggest questions in condensed matter physics:**The nature of high-temperature superconductors Quantum magnetism, spin liquids Strongly correlated, strongly interacting systems**Title**How to get strong interactions? Pair A-B Particle A Particle B**Title**Resonant interactions have infinite strength Pair A-B Particle A Particle B • Unitarity limited interactions: • Pairing in ultracold fermions • Relevant to quark-gluon plasmas**E**Free atoms Molecule Magnetic field Feshbach resonance**Disclaimer: Drawing is schematic and does not distinguish**nuclear and electron spin. E Free atoms Molecule Magnetic field Feshbach resonance**Two atoms ….**E Free atoms Molecule Magnetic field Feshbach resonance**… form an unstable molecule**E Free atoms Molecule Magnetic field Feshbach resonance**… form a stable molecule**E Free atoms Molecule Magnetic field Feshbach resonance**Atoms attract each other**E Free atoms Molecule Magnetic field Feshbach resonance**Atoms repel each other**Atoms attract each other E Free atoms Molecule Magnetic field Feshbach resonance**Atoms repel each other**Atoms attract each other Force between atoms Scattering length Magnetic field Feshbach resonance**Title**Observation of High-Temperature Superfluidity in Ultracold Fermi Gases**At absolute zero temperature …**Bose-Einstein condensation atoms as waves superfluidity Fermi sea: Atoms are not coherent No superfluidity Bosons Particles with an even number of protons, neutrons and electrons Fermions Particles with an odd number of protons, neutrons and electrons**Pairs of fermions**Particles with an even number of protons, neutrons and electrons Two kinds of fermions Fermi sea: Atoms are not coherent No superfluidity**At absolute zero temperature …**Pairs of fermions Particles with an even number of protons, neutrons and electrons Bose-Einstein condensation atoms as waves superfluidity Two kinds of fermions Particles with an odd number of protons, neutrons and electrons Fermi sea: Atoms are not coherent No superfluidity**Weak attractive interactions**Cooper pairs larger than interatomic distance momentum correlations BCS superfluidity Two kinds of fermions Particles with an odd number of protons, neutrons and electrons Fermi sea: Atoms are not coherent No superfluidity**Electron pairs**Atom pairs Bose Einstein condensate of molecules BCS Superconductor**Atoms attract each othera<0**Atoms repel each othera>0 Energy Atoms Molecules Magnetic field Molecules are unstable Atoms form stable molecules BCS-limit: Condensation of long-range Cooper pairs BEC of Molecules: Condensation of tightly bound fermion pairs**Atom pairs**Bose Einstein condensate of molecules BCS superfluid**BCS superfluid**Molecular BEC**Magnetic field**BCS superfluid Molecular BEC**Crossover superfluid**BCS superfluid Molecular BEC**Fermi energy**Fermi temperature (density)2/3 high Tc superfluid 0.3 High-temperature superfluidity at 100 nK? Transition temperature Binding energy of pairs 10-5 … 10-4normal superconductors 10-3superfluid 3He 10-2high Tc superconductors Scaled to the density of electrons in a solid:Superconductivity far above room temperature!**Preparation of an interacting Fermi system in Lithium-6**Optical trapping @ 1064 nm naxial = 10-20 Hznradial= 50–200 Hz Etrap = 0.5 - 5 mK States |1> and |2> correspond to |> and |>**Title**How to show that these gases are superfluid?**Quantized circulation**Quantization: Integer number of matter waves on a circle

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