Observation of Coupled Vortex Lattices in a Mass-Imbalance Bose and Fermi Superfluid Mixture

Abstract

The superfluid mixture of interacting Bose and Fermi species is a remarkable many-body quantum system. Dilute degenerate atomic gases, especially for two species of distinct masses, are excellent candidates for exploring fundamental features of superfluid mixture. However, producing a mass-imbalance Bose-Fermi superfluid mixture, providing an unambiguous visual proof of two-species superfluidity and probing inter-species interaction effects remain challenging. Here, we report the realization of a two-species superfluid of lithium-6 and potassium-41. By rotating the dilute gases, we observe the simultaneous existence of vortex lattices in both species, and thus present a definitive visual evidence for the simultaneous superfluidity of the two species.Pronounced effects of the inter-species interaction are demonstrated through a series of precision measurements on the formation and decay of two-species vortices. Our system provides a new platform for studying novel macroscopic quantum phenomena in vortex matter of interacting species.

A Dual-Species Bose-Einstein Condensate with Attractive Interspecies Interactions

“…Ultracold atomic mixtures, formed by atoms of the same species in different spin states, or as different isotopes or elements, enable us to address a wide variety of problems in many-body physics. They have been largely used to investigate phase-transitions [1][2][3][4], multi-component superfluidity [5][6][7], topological defects [8][9][10], magnetism [11][12][13], ultracold chemistry [14] and impurity and polaron physics [15][16][17]. Most of these phenomena are accessible thanks to the ability to control the sign and strength of interactions, opening the way to the study of unconventional matter phases.…”

Narrow-linewidth cooling of $$^{6}$$ 6 Li atoms using the 2S-3P transition

“…The obtained 8.1 × 10 8 atoms with a temperature of 296 µK at a 198 G/cm magnetic field gradient in the science chamber is an excellent starting point for the production of large 6 Li quantum degenerate gases. In the near future, we will combine the UV MOT of 6 Li with the gray molasses of 41 K to achieve an even larger two-species Bose-Fermi superfluid [33].…”

An ultracold, optically trapped mixture of 87Rb and metastable 4He atoms

“…Among the possible solutions are the application of special optical dipole trap geometries that allow for strong vertical confinement in a shallow trap (see e.g. [10]), or the addition of an optical dipole beam that selectively supports the heavy species [73]. Another approach is to add a magnetic field gradient that will provide an additional species-dependent force [74].…”

“…Most mixtures of chemically distinct atomic species consist of alkali-metals: Li+Na [1], Li+K [10,20,21], Li+K+Rb [22], Li+Rb [23], Li+Cs [24][25][26], Na+K [27], Na+Rb [28], K+Rb [2,29,30], K+Cs [31], Rb+Cs [32,33]. These experimental efforts laid the foundation of the creation of ultracold heteronuclear ground-state molecules, which posses a large permanent dipole moment: KRb [4], RbCs [5,6], NaK [7] and NaRb [8].…”

“…Ultracold mixtures of distinct atomic species serve for many scientific goals: sympathetic cooling of atomic species for which evaporative cooling is inefficient [1][2][3], creation of ultracold polar molecules [4][5][6][7][8], exploring many-body physics in quantum degenerate Bose-Bose, Bose-Fermi and Fermi-Fermi atomic mixtures [9][10][11], studying impurities immersed in Bose or Fermi gases [12][13][14][15][16], heteronuclear few-body physics [17,18], and testing universality of free-fall [19].…”