Thermodynamic properties of matter generally depend on the details of interactions between its constituent parts. However, in a unitary Fermi gas where the scattering length diverges, thermodynamics is determined through universal functions that depend only on the particle density and temperature. By using only the general form of the equation of state and the equation of force balance, we measured the local internal energy of the trapped gas as a function of these parameters. Other universal functions, such as those corresponding to the Helmholtz free energy, chemical potential, and entropy, were calculated through general thermodynamic relations. The critical parameters were also determined at the superfluid transition temperature. These results apply to all strongly interacting fermionic systems, including neutron stars and nuclear matter.

We observed an enhanced atom-dimer loss 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 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 energy levels of |23> dimers and the ground and first excited Efimov trimers. We found that the locations of these peaks disagree with universal theory predictions, in a way that cannot be explained by nonuniversal two-body properties. We constructed theoretical models that characterize the nonuniversal three-body physics of three-component 6Li atoms in the low-energy domain.

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.About forty years ago, V. Efimov predicted that the existence of universal trimer states known as the Efimov states, in a three-body system with resonant short-range interactions [1]. Such universal states are characterized only by the two-body scattering lengths for each pair of particles and a three-body parameter fixed by short-range physics. Owing to magnetic Feshbach resonances [2], ultracold atomic systems turned out to be the first systems where the Efimov effect was observed conclusively. Since the first experimental evidence in an ultracold cesium gas [3], general properties of few-body systems near unitarity such as the universal scaling laws [4] were confirmed in many ultracold bosonic systems [5-9] and a three-component fermionic gas of 6 Li [10][11][12][13][14], via the inelastic collision enhancements and minima occurring at particular intensities of an externally-applied magnetic field. Although these features are qualitatively explained by Efimov's universal theory (UT) [4], their relative positions of loss features are shifted significantly from universal predictions. For example, the shift of the atom-dimer loss peaks from that expected from the three-body loss peaks [5,13,14] and the notable discrepancies in properties of the Efimov resonances between regions of positive and negative scattering lengths [8] do not seem to be consistent with a fixed three-body parameter. Therefore, the precise determination of the three-body parameter is crucial to understand these systems.To understand the atom-dimer loss feature in the threecomponent gas of 6 Li, we constructed a nonuniversal model by taking into account the energy dependence of the scattering length due to finite-range corrections [13]. This two-body physics correction still does not explain the atom-dimer loss feature that we observed experimentally. We then introduced an energy-dependent three-body parameter Λ which phenomenologically reproduces all the experimental data of the three-body loss and the atomdimer loss in the three-component mixture of 6 Li atoms. [13,15]. However, these three-body and atom-dimer loss measurements provide information on Λ only at the points where the trimer energy level vanishes upon dissociation or meets a dimer energy level. Thus, it has been desirable to directly measure the binding energy of the Efimov trimers to fully determine the three-body parameter and the validity of the model. Recently, T. Lompe et.al.[16] demonstrated a radiofrequency (RF) association of the Efimov trimer state in the three-component mixture of 6 Li atoms. This method constitutes the most direct o...

We report the experimental observation of rectified momentum transport for a Bose-Einstein Condensate kicked at the Talbot time (quantum resonance) by an optical standing wave. Atoms are initially prepared in a superposition of the 0 and −2 k l momentum states using an optical π/2 pulse. By changing the relative phase of the superposed states, a momentum current in either direction along the standing wave may be produced. We offer an interpretation based on matter wave interference, showing that the observed effect is uniquely quantum.The current interest in rectified atomic diffusion, or atomic ratchets, may be traced back to fundamental thermodynamical concerns [1] and also the desire to understand the so-called "Brownian motors" linked to directed diffusion on a molecular scale [2,3]. Abstractly, the ratchet effect may be defined as the inducement of directed diffusion in a system subject to unbiased perturbations due to a broken spatio-temporal symmetry.Given the scale on which such microscopic ratchets must work, it is not surprising that the concept of quantum ratchets has recently augmented this area of investigation. The addition of quantum effects such as tunneling gives rise to new ratchet phenomena such as current reversal [4]. Whilst early quantum ratchet investigations, both theoretical and experimental, have focussed on the role of dissipative fluctuations in driving a ratchet current [5], recent theory has considered the possibility of Hamiltonian ratchets, where the diffusion arises from Hamiltonian chaos rather than stochastic fluctuations [6]. This has lead to proposals [7,8] and even an experimental realisation [9] for ratchet systems realised using atom optics, in the context of the atom optics kicked rotor [10] where periodic pulses from an optical standing wave kick atoms into different momentum states.It is generally accepted that a ratchet effect cannot be produced without breaking the spatio-temporal symmetry of the kicked rotor system. In Ref.[9], a rocking sine wave potential was combined with broken time symmetry of the kicking pulses to effectively realise such a system in an experiment. Other schemes involve the use of quantum resonance (QR) to drive the ratchet effect. At QR, atoms typically exhibit linear momentum growth symmetrical about the initial mean momentum. However it has been suggested that merely breaking the spatial symmetry of the kicked rotor at QR may be sufficient to produce a ratchet current [11]. In this letter we present the first experimental evidence of such a resonant ratchet effect in which the underlying mechanism is purely quantum. Our system uses a Bose-Einstein condensate (BEC) kicked by an optical standing wave [12], but there is no asymmetry in either the kicking potential * Electronic address: mark@ils.uec.ac.jp or the period of the kicks, (which is set to the Talbot time T T corresponding to quantum resonance [13]). Rather, the observed directed diffusion is a property of the initial atomic wavefunction (which we prepare before kicking) in the presenc...

We have observed p-wave Feshbach molecules for all three combinations of the two lowest hyperfine spin states of 6Li. By creating a pure molecular sample in an optical trap, we measured the inelastic collision rates of p-wave molecules. We have also measured the elastic collision rate from the thermalization rate of a breathing mode which was excited spontaneously upon molecular formation.