Ultracold Feshbach molecules in an orbital optical lattice

Abstract

Quantum gas systems provide a unique experimental platform to study a fundamental paradigm of quantum many-body physics: the crossover between Bose-Einstein condensed (BEC) molecular pairs and Bardeen Cooper Schrieffer (BCS) superfluidity. Some studies have considered quantum gas samples confined in optical lattices, however, focusing on the case, when only the lowest Bloch band is populated, such that orbital degrees of freedom are excluded. In this work, for the first time, ultracold Feshbach molecules of fermionic ${}^{40}K$ atoms are selectively prepared in the second Bloch band of an optical square lattice, covering a wide range of interaction strengths including the regime of unitarity. Binding energies and band relaxation dynamics are measured by means of a method resembling mass spectrometry. The longest lifetimes arise for strongly interacting Feshbach molecules at the onset of unitarity with values around 300 ms for the lowest band and 100 ms for the second band. In the case of strong confinement in a deep lattice potential, we observe bound dimers also for negative values of the s-wave scattering length, extending previous findings for molecules in the lowest band. Our work prepares the stage for orbital BEC-BCS crossover physics.

7 pages, 5 figures

References in corpus (9)

• Ultracold atomic gases in optical lattices: mimicking condensed matter physics and beyond
• Crossover from a molecular Bose-Einstein condensate to a degenerate Fermi gas
• Evidence for Superfluidity of Ultracold Fermions in an Optical Lattice
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• Diatomic molecules in ultracold Fermi gases - Novel composite bosons
• Potassium ground state scattering parameters and Born-Oppenheimer potentials from molecular spectroscopy
• Observation of unitary p-wave interactions between fermions in an optical lattice
• Quantum degenerate Fermi gas in an orbital optical lattice

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• Two-Body Kapitza-Dirac Scattering of One-Dimensional Ultracold Atoms
• Efficient shortcuts-to-adiabaticity for loading an ultracold Fermi gas into higher orbital bands of one-dimensional optical lattice
• Collisional scattering of strongly interacting D-band Feshbach molecules in optical lattices