C6 coefficients for interacting Rydberg atoms and alkali-metal dimers

Abstract

We study the van der Waals interaction between Rydberg alkali-metal atoms with fine structure (n 2 Lj; L ≤ 2) and heteronuclear alkali-metal dimers in the ground rovibrational state (X 1 Σ + ; v = 0, J = 0). We compute the associated C6 dispersion coefficients of atom-molecule pairs involving 133 Cs and 85 Rb atoms interacting with KRb, LiCs, LiRb, and RbCs molecules. The obtained dispersion coefficients can be accurately fitted to a state-dependent polynomial O(n 7 ) over the range of principal quantum numbers 40 ≤ n ≤ 150. For all atom-molecule pairs considered, Rydberg states n 2 Sj and n 2 Pj result in attractive 1/R 6 potentials. In contrast, n 2 Dj states can give rise to repulsive potentials for specific atom-molecule pairs. The interaction energy at the LeRoy distance approximately scales as n −5 for n > 40. For intermediate values of n 40, both repulsive and attractive interaction energies in the order of 10 − 100 µK can be achieved with specific atomic and molecular species. The accuracy of the reported C6 coefficients is limited by the quality of the atomic quantum defects, with relative errors ∆C6/C6 estimated to be no greater than 1% on average.

Laser-assisted binding of ultracold polar molecules with Rydberg atoms in the van der Waals regime

“…For every point we obtain an error bar that represents different choices of R c . We confirm that the numerical binding energies E −1 do not exceed the theoretical limit (dashed lines) and decrease with increasing n, following the scaling C 6 ∼ n 7 [28]. The numerical resolution of our bound state energies is about 3.1 kHz, mostly constrained by the implementation of the Fourier grid [36].…”

“…Here we focus on the PA rate that describes the laser-assisted binding of a 85 Rb ground state atom (5 2 S 1/2 ) and a KRb molecule in the ground rovibrational state ( 1 Σ + , v = 0, J = 0) into a long-range atom-molecule trimer state that correlates asymptotically with the atomic Rydberg state n 2 L j , where L is the atomic orbital angular momentum and j the total electronic angular momentum. Spin-orbit coupling in the atomic Rydberg manifold is taken into account [28]. The laser frequencies in the two-color excitation scheme are chosen such that the formation of long-range atom-molecule trimers is most efficient at interparticle distances that far beyond the Le Roy radius of the asymptotic Rydberg state.…”

“…van der Waals coefficients for the interaction of KRb in the rovibrational ground state with a Rb atom in the n 2 L j Rydberg level are taken from Ref. [28]. We extend the van der Waals potential up to an arbitrary cutoff distance R c below the atomic Le Roy radius (R c < R LR ), where we then introduce a semi-infinite barrier.…”

“…In this regime the interaction between molecules and Rydberg atoms is dominated by the van der Waals potential V (r) = C 6 /r 6 , where the C 6 is a state-dependent van der Waals coefficient. We recently computed C 6 coefficients for a large set of alkali-metal Rydberg levels and selected alkali-dimers in their rovibrational ground state [28]. For attractive atom-molecule potentials in an atomic Rydberg channel (C 6 < 0), we expect the laser excitation lineshape of the Rydberg level to be sensitive to the formation of long-range atom-molecule trimer bound states near threshold via two-photon photoassociation [29,30].…”

Strong zero-field Förster resonances in K-Rb Rydberg systems

“…A two-species system of rubidium and cesium (Rb-Cs) atoms has been recently proposed as a promising approach for qubit systems with suppressed cross talk between computational and measurement qubits [32,36]. Dimer states and dispersion coefficients in K-Rb Rydberg systems have also been theoretically studied [37,38]. K-Rb in particular offers the possibility to explore effects due to the bosonic ( 85 Rb, 87 Rb, 39 K, 41 K) and the fermionic ( 40 K) quantum statistics of the atoms.…”