Emergence of chaotic scattering in ultracold Er and Dy


Now in PRX! We show that for ultracold magnetic lanthanide atoms (Er and Dy) chaotic scattering emerges due to a combination of anisotropic interaction potentials and Zeeman coupling under an external magnetic field. The scattering is studied in a collaborative experimental and theoretical effort, involving our group, the Stuttgart Dy Group led by T. Pfau and the theory colleagues S. Kotochigova and E. Tiesinga in the USA.  [more]

Observation of Fermi surface deformation in a dipolar quantum gas


Now in Science! In the presence of isotropic interactions, the Fermi surface of an ultracold Fermi gas is spherical. Introducing anisotropic interactions can deform it. This effect is subtle and challenging to observe experimentally. We report the observation of such a Fermi surface deformation in a degenerate dipolar Fermi gas of erbium atoms. The deformation is caused by the interplay between strong magnetic dipole-dipole interaction and the Pauli exclusion principle. We demonstrate the many-body nature of the effect and its tunability with the Fermi energy. Our observation provides a basis for future studies on anisotropic many-body phenomena in normal and superfluid phases. [more]

Quantum Chaos in Ultracold Collisions of Erbium


We have studied the scattering behavior of ultracold Er atoms and observed an enormous number of Fano-Feshbach scattering resonances and demonstrate high correlation in the spectra, underlying chaotic scattering between the particles. This work, now published in NATURE,  is a joint effort between our group, John L. Bohn from JILA (Boulder, Colorado),  and the team of Svetlana Kotochigova at Temple University (USA). Nice media coverage (in italian) from the MEDIA INAF. [more]

Reaching Fermi Degeneracy via Universal Dipolar Scattering


We report on the creation of the first degenerate dipolar Fermi gas of erbium atoms. We force evaporative cooling in a fully spin-polarized sample down to temperatures as low as 0.2 times the Fermi temperature. The strong magnetic dipole-dipole interaction enables elastic collisions between identical fermions even in the zero-energy limit. The measured elastic scattering cross section agrees well with the predictions from the dipolar scattering theory, which follow a universal scaling law depending only on the dipole moment and on the atomic mass. Our approach to quantum degeneracy proceeds with very high cooling efficiency and provides large atomic densities, and it may be extended to various dipolar systems. [more]

Bose-Einstein Condensation of Erbium


We report on the achievement of Bose-Einstein condensation of erbium atoms and on the observation of magnetic Feshbach resonances at low magnetic fields. By means of evaporative cooling in an optical dipole trap, we produce pure condensates of Er168, containing up to 7×104 atoms. Feshbach spectroscopy reveals an extraordinary rich loss spectrum with six loss resonances already in a narrow magnetic-field range up to 3 G. Finally, we demonstrate the application of a low-field Feshbach resonance to produce a tunable dipolar Bose-Einstein condensate and we observe its characteristic d-wave collapse. [more]