Measurement of an Efimov trimer binding energy in a three-component mixture of 6Li

The binding energy of an Efimov trimer state was precisely determined via radio-frequency association. It is found that the measurement results significantly shift with temperature, but that the shift can be made negligible at the lowest temperature in our experiment. The obtained trimer binding energy reveals a significant deviation from the nonuniversal theory prediction based on a three-body parameter with a monotonic energy dependence.Comment: 4 pages, 4 figure

Non-universal Efimov Atom-Dimer Resonances in a Three-Component Mixture of 6Li

We observed an enhanced atom-dimer relaxation due to the existence of Efimov states in a three-component mixture of 6Li atoms. We measured the magnetic-field dependence of the atom-dimer loss coefficient in the mixture of atoms in state |1> and dimers formed in states |2> and |3>, and found two peaks corresponding to the degeneracy points of the |23> dimer energy level and energy levels of Efimov trimers. We found that the locations of these peaks disagree with universal theory predictions, in a way that cannot be explained by non-universal two-body properties. We constructed theoretical models that characterize the non-universal three-body physics of three-component 6Li atoms in the low energy domain.Comment: 5 pages, 3 figure

Critical Temperature and Condensate Fraction of a Fermion Pair Condensate

We report on measurements of the critical temperature and the temperature dependence of the condensate fraction for a fermion pair condensate of 6Li atoms. The Bragg spectroscopy is employed to determine the critical temperature and the condensate fraction after a fast magnetic field ramp to the molecular side of the Feshbach resonance. Our measurements reveal the level-off of the critical temperature and the limiting behavior of condensate fraction near the unitarity limit

ボース凝縮体を用いたアトムチップ上での干渉計

In this thesis, trapped-atom interferometers are investigated using a Bose-Einstein condensate(BEC) on an atom chip in order to provide long coherence times.For the interferometer, a fast chip-based BEC production system was developed. By using astandard six-beam magneto-optical trap and the technique of light-induced atom desorption forloading, 3 ￡ 107 87Rb atoms are collected within 1 s and loaded into a small-volume magneticpotential of the chip with high efficiency. The resultant large atomic density in the potentialmakes it possible to realize fast and efficient evaporative cooling. Using this method, a condensateof 3 ￡ 103 atoms is realized within a total time of 3 s.A Mach-Zehnder-type condensate interferometer was investigated in a magnetic potentialby using optical Bragg diffractions. A phase shift and contrast degradation of the interferencefringe, which depend on the magnetic potential and the atomic density, were investigated indetail to determine the dephasing mechanism. We show that the trapping potential and thecondensate atom-atom interaction plays an important role in inducing the dephasing of theinterference signals, and that the limitation of the coherence time is an inevitable result of thedephasing.Additionally, a novel dephasing-free trapped-atom interferometer was proposed and demonstratedby using a BEC trapped in a harmonic magnetic potential. Dephasing of the wave packetdue to the magnetic potential is cancelled by setting the interrogation time equal to the oscillationperiod of the harmonic potential. The harmonic potential also helps to cancel dephasingdue to the atom-atom interaction of the condensate. An interference signal with a fringe contrastof 30%was observed at an interrogation time of 58ms. With a longer interrogation time of about100ms, the separated condensates still show high spatial coherence without dephasing, but theinterference fringe is washed out by external vibrations. The coherence time realized in thisthesis is the longest time in the condensate interferometer based on optical Bragg diffractionsso far.電気通信大学200