Anisotropic light shift and magic polarization of the intercombination line of dysprosium atoms in a far-detuned dipole trap

Abstract

We characterize the anisotropic differential ac-Stark shift for the Dy 626 nm intercombination transition, induced in a far-detuned 1070 nm optical dipole trap, and observe the existence of a "magic polarization" for which the polarizabilities of the ground and excited states are equal. From our measurements we extract both the scalar and tensorial components of the dynamic dipole polarizability for the excited state, α s E = 188(12) α0 and α t E = 34(12) α0, respectively, where α0 is the atomic unit for the electric polarizability. We also provide a theoretical model allowing us to predict the excited state polarizability and find qualitative agreement with our observations. Furthermore, we utilize our findings to optimize the efficiency of Doppler cooling of a trapped gas, by controlling the sign and magnitude of the inhomogeneous broadening of the optical transition. The resulting initial gain of the collisional rate allows us, after forced evaporation cooling, to produce a quasi-pure Bose-Einstein condensate of 162 Dy with 3 × 10 4 atoms.

Observation of a narrow inner-shell orbital transition in atomic erbium at 1299 nm

“…Importantly, the dependence of α(ω) on u and θ p allows to tune α(ω) for a fixed ω. This additional tunability on the polarization of the trapping light increases the possibilities for magictrapping conditions [64,65]. In Figure 5(c) we plot α(ω) of |g and |e for both, π-and σ − -polarization.…”

“…Moreover, in erbium, as in other lanthanides, the total polarizability is anisotropic with important vectorial and tensorial contributions. This allows for instance an orientation tuning of the optical dipole potential [56,63,64]. In detail, the atomic polarizability α(ω) of an atom with non-zero angular-momentum J, that is placed in an external laser field oscillating at a frequency ω, can be expressed as:…”

New opportunites for interactions and control with ultracold lanthanides

“…However, in the last years, tremendous progress has been made in calculating the atomic polarizability of various lanthanides; see e. g. [75][76][77][78][79]. In experiments, the scalar, vectorial, and tensorial dynamical polarizability at specific wavelengths have been measured for erbium [80], dysprosium [81][82][83][84], and thulium [79,85]. The anisotropic polarizability and spindependent atom-light interaction have been then used to realize "tune-out" [81] and "magic [13,83] wavelength conditions between ground and excited states, as well as techniques for control of spin and motional dynamics, discussed in the following section.…”

Enhanced Magnetic Sensitivity with Non-Gaussian Quantum Fluctuations

“…1. We first prepare a gas of 1.0(2) × 10 5 atoms of 162 Dy at a temperature T = 1.1(2) µK, using standard cooling techniques [42]. The atoms are initially spin-polarized in the absolute ground state |m = −J z , under a quantization field B = Bẑ, with B = 60.6(3) mG. We shine on the atoms an off-resonant laser beam inducing spin-dependent light shifts thanks to the proximity to the narrow 626-nm optical transition (natural linewidth Γ 0.85 µs −1 ).…”