Magnetic tuning of electric dipole moments and dipolar interactions of alkali-dimer molecules*

We show that the electric dipole moments (EDMs) of ground-state alkali-dimer molecules such as KRb(X¹Σ) can be efficiently tuned over a wide dynamic range (including zero) with an external dc magnetic field even at zero external dc electric field. The magnetic field tunability is enabled by the electric quadrupole interaction, which couples hyperfine sublevels within the first excited rotational states at low magnetic fields. The admixture generates non-zero transition dipole moments with hyperfine sublevels in the ground rotational states, which are otherwise suppressed at large magnetic fields. The tunability of the EDMs via magnetic switching opens up new opportunities for Hamiltonian engineering and interaction control of lattice-confined ultracold polar molecules.