Highly elastic collisions of ultracold asymmetric top molecules in a static electric field

Abstract

We propose that the application of static electric fields to reactive CaNH$_2$ molecules can result in large ratios of elastic to lossy collisions at ultracold temperatures. In the first rotationally excited manifold, the asymmetric top structure of CaNH$_2$ results in a $\approx 226$ MHz splitting of the opposite parity $K$-doublet states. This modest splitting allows electric fields below a kilovolt per centimeter to polarize the molecules and induce long-range dipole-dipole interactions. By increasing the electric field, we find that dipole-dipole attraction can become sufficiently large to induce weakly bound octatomic field-linked states of [CaNH$_2$]$_2$. In the absence of these field-linked states, we identify select molecular states where dipolar interactions allow elastic collisions to dominate over lossy collisions by up to three orders of magnitude, while maintaining loss rate coefficients at the $10^{-14}$ cm$^3$s$^{-1}$ level. These results establish that evaporative cooling is a viable route to quantum degenerate gases of laser coolable asymmetric top molecules. Access to such low entropy ensembles of asymmetric top molecules holds promise to push the frontiers of quantum simulation, state-resolved chemistry, and searches for beyond the Standard Model physics.