Pauli paramagnetism of an ideal Fermi gas

We show how to use trapped ultracold atoms to measure the magnetic susceptibility of a two-component Fermi gas. The method is illustrated for a non-interacting gas of $^6$Li, using the tunability of interactions around a wide Feshbach resonances. The susceptibility versus effective magnetic field is directly obtained from the inhomogeneous density profile of the trapped atomic cloud. The wings of the cloud realize the high field limit where the polarization approaches 100%, which is not accessible for an electron gas.Comment: 5 pages, 4 figure

Spontaneous Symmetry Breaking of Population between Two Dynamic Attractors in a Driven Atomic Trap: Ising-class Phase Transition

We have observed spontaneous symmetry breaking of atomic populations in the dynamic phase-space double-potential system, which is produced in the parametrically driven magneto-optical trap of atoms. We find that the system exhibits similar characteristics of the Ising-class phase transition and the critical value of the control parameter, which is the total atomic number, can be calculated. In particular, the collective effect of the laser shadow becomes dominant at large atomic number, which is responsible for the population asymmetry of the dynamic two-state system. This study may be useful for investigation of dynamic phase transition and temporal behaviour of critical phenomena.Comment: 4 pages, 4 figure

Deviation from Universality in Collisions of Ultracold [superscript 6] Li[subscript 2] Molecules

Collisions of [superscript 6]Li[subscript 2] molecules with free [superscript 6]Li atoms reveal a striking deviation from universal predictions based on long-range van der Waals interactions. Li[subscript 2] closed-channel molecules are formed in the highest vibrational state near a narrow Feshbach resonance and decay via two-body collisions with Li[subscript 2], Li, and Na. For Li[subscript 2]+Li[subscript 2] and Li[subscript 2]+Na, the decay rates agree with the universal predictions of the quantum Langevin model. In contrast, the rate for Li[subscript 2]+Li is exceptionally small, with an upper bound 10 times smaller than the universal prediction. This can be explained by the low density of available decay states in systems of light atoms [G. Quéméner, J.-M. Launay, and P. Honvault, Phys. Rev. A 75 050701 (2007)], for which such collisions have not been studied before.United States. Air Force Office of Scientific Research. Multidisciplinary University Research InitiativeUnited States. Army Research Office. Multidisciplinary University Research InitiativeNational Science Foundation (U.S.)United States. Office of Naval ResearchUnited States. Army Research Office (Grant W911NF-07-1-0493)United States. Defense Advanced Research Projects Agency. Optical Lattice Emulator ProgramNatural Sciences and Engineering Research Council of Canad

Comparative radiologic study of bone density and cortical thickness of donor bone used in mandibular reconstruction

Objective: The aim of this study was to compare the total cancellous bone density, bone-implant interface density, and cortical thickness of 6 donor bone types commonly used in oral and maxillofacial reconstruction. Methods: A total of 120 bones from 20 Korean adults—including iliac bones, fibulas, cranial bones, scapulas, ribs, and clavicles—were selected. The implant recipient site was determined by the shape, contour, and anatomical limitations of the bones. The serial cross-sectional images of each bone were then acquired through computed tomography. Total cancellous bone density, bone-implant interface density around the imaginary implant fixture, and the cortical thickness along both sides of the imaginary fixture on each cross-sectional image were evaluated and compared. Results: The cancellous bone density of each donor bone type had a statistically significant difference. The cranial bone showed the highest cancellous bone density, followed by the iliac bone, clavicle, scapula, rib, and fibula (P < .05). The bone-implant interface density of the cranial bone, clavicle, fibula, and scapula each belonged to the same Duncans group, whereas the rib and iliac bone showed lower bone-implant interface density. In average cortical thickness, the scapula and fibula had a thicker cortex surrounding the imaginary implant than the other bones, and the rib had the thinnest cortex. Conclusion: Although more extensive testing is needed to explain the clinical implications of these results, the findings of this study may help clinicians choose the most appropriate donor bone.Supported in part by 2001 BK21 project for Medicine, Dentistry and Pharmacy

Chip-Scale Ultra-Low Field Atomic Magnetometer Based on Coherent Population Trapping

We report a chip-scale atomic magnetometer based on coherent population trapping, which can operate near zero magnetic field. By exploiting the asymmetric population among magnetic sublevels in the hyperfine ground state of cesium, we observe that the resonance signal acquires sensitivity to magnetic field in spite of degeneracy. A dispersive signal for magnetic field discrimination is obtained near-zero-field as well as for finite fields (tens of micro-tesla) in a chip-scale device of 0.94 cm3 volume. This shows that it can be readily used in low magnetic field environments, which have been inaccessible so far in miniaturized atomic magnetometers based on coherent population trapping. The measured noise floor of 300 pT/Hz1/2 at the zero-field condition is comparable to that of the conventional finite-field measurement obtained under the same conditions. This work suggests a way to implement integrated atomic magnetometers with a wide operating range

Formation of ultracold fermionic NaLi Feshbach molecules

We describe the formation of fermionic NaLi Feshbach molecules from an ultracold mixture of bosonic [superscript 23]Na and fermionic [superscript 6]Li. Precise magnetic field sweeps across a narrow Feshbach resonance at 745 G result in a molecule conversion fraction of 5% for our experimental densities and temperatures, corresponding to a molecule number of 5×10[superscript 4]. The observed molecular decay lifetime is 1.3 ms after removing free Li and Na atoms from the trap. Due to its extremely low reactivity, NaLi molecules in the ground state will have a much longer lifetime than KRb.United States. Air Force Office of Scientific Research. Multidisciplinary University Research InitiativeNational Science Foundation (U.S.)United States. Office of Naval ResearchUnited States. Army Research Office (Grant W911NF-07-1-0493)United States. Defense Advanced Research Projects Agency. Optical Lattice Emulator ProgramNatural Sciences and Engineering Research Council of Canada (NSERC

Compressibility of an ultracold Fermi gas with repulsive interactions

Fermi gases with repulsive interactions are characterized by measuring their compressibility as a function of interaction strength. The compressibility is obtained from in-trap density distributions monitored by phase-contrast imaging. For interaction parameters k[subscript F]a>0.25, fast decay of the gas prevents the observation of equilibrium profiles. For smaller interaction parameters, the results are adequately described by first-order perturbation theory. We have developed a phase-contrast imaging method that compensates for dispersive distortions of the images.National Science Foundation (U.S.).United States. Office of Naval ResearchUnited States. Office of Naval Research. Multidisciplinary University Research InitiativeUnited States. Army Research Office (grant no. W911NF-07-1-0493