Observation of low-field Fano-Feshbach resonances in ultracold gases of dysprosium

We report the observation of resonancelike loss in the trap population of ultracold dysprosium as a function of magnetic field, which we attribute to anisotropy-induced Fano-Feshbach resonances arising from Dy's large magnetic dipole moment and nonzero electronic orbital angular momentum. We recorded these resonances for four different isotopes, three bosonic and one fermionic, over a field range of 0–6 G and show that the number of resonances changes significantly as a function of temperature, even in the nK regime. Most of the observed resonances are of very narrow width. The fermionic isotope, unlike its bosonic counterparts, possesses nonzero nuclear spin and exhibits a much higher density of resonances.

Figure 1

Atom-loss spectrum for bosonic ${}^{164}$Dy. The top panel displays data taken with an $\sim 420$ nK sample showing a large number of Fano-Feshbach resonances. The lower panel shows a measurement of the same isotope ${}^{164}$Dy at higher temperature $\sim 800$ nK. New resonances appear in the warmer sample. The arrows show the position of the resonances obtained by fitting a Gaussian function to each individual feature. Experimental parameters in main text.

Figure 2

Atom-loss spectra as a function of magnetic field for the bosonic isotopes ${}^{160}$Dy (top) and ${}^{162}$Dy (bottom). The spectra lack the broad feature observed in ${}^{164}$Dy (Fig. 1), but are otherwise qualitatively similar. The arrows show the position of the resonances obtained by fitting a Gaussian function to each individual feature. Experimental parameters in main text.

Figure 3

Atomic-loss spectrum for the fermionic isotope ${}^{161}$Dy. The top panel shows a full scan over 6 G, whereas the lower panel shows a close-up with much higher resolution. As apparent from the close-up plot, the ultranarrow features in the top panel are scattering features. The arrows in the lower panel show the positions of the resonances deduced from the upper panel; the arrows in black (dashed) mark false resonances, i.e., statistical fluctuations in the upper panel not reproduced in the lower panel with high-resolution data. Experimental parameters in main text.