Spinor Bose-Einstein condensates of rotating polar molecules

Abstract

We propose a scheme to realize a pseudospin-1/2 model of the 1 Σ(v = 0) bialkali polar molecules with the spin states corresponding to two sublevels of the first excited rotational level. We show that the effective dipole-dipole interaction between two spin-1/2 molecules couples the rotational and orbital angular momenta and is highly tunable via a microwave field. We also investigate the ground state properties of a spin-1/2 molecular condensate. A variety of nontrivial quantum phases, including the doubly-quantized vortex states, are discovered. Our scheme can also be used to create spin-1 model of polar molecules. Thus, we show that the ultracold gases of bialkali polar molecules provide a unique platform for studying the spinor condensates of rotating molecules. [11,12], cold controlled chemistry [13,14], and quantum simulation [15][16][17]. Particularly, from the condensed matter perspective, the large permanent electric dipole moment and the ability to control the hyperfine states within a single rovibrational level [18,19] make ultracold polar molecules an ideal platform for investigating strongly correlated many-body physics [20][21][22]. So far, the dipolar spin-exchange interactions [23] and the many-body dynamics [24] have been experimentally observed in lattice-confined ultracold KRb gases.For rotating molecules, the net dipole moment in the lab frame vanishes in the absence of a dc electric field. Hence, in most theoretical many-body studies, a strong dc electric field is assumed to align polar molecules. Consequently, the rotational degrees of freedom is frozen. Even though, there exist multicomponent models by utilizing different rotational states, the number of molecules in each rotational state is independently conserved by the interactions. On the contrary, the spin-exchange contact interaction in atomic spinor Bose-Einstein condensates (BECs) results in rich magnetic phenomena [25][26][27]. Of particular interest, the magnetic dipole-dipole interaction (DDI) gives rise to spontaneous spin textures in dipolar spinor BECs [28][29][30][31].In this Letter, we show that a bialkali polar molecule in the electronic and vibrational ground state can be modeled as a pseudospin-1/2 molecule with the spin states corresponding to two hyperfine sublevels of the first excited rotational level. Remarkably, the effective DDI between molecules contains a rotation-orbit coupling term that is capable of inducing spin mixing. Thus a BEC formed by these spin-1/2 molecules represents a spinor BEC, instead of a two-component one. We also study the ground state phases of the spin-1/2 molecular BEC and demonstrate that rotation-orbit-coupled DDI gives rise to the doubly quantized vortex phases. Although

Extending Rotational Coherence of Interacting Polar Molecules in a Spin-Decoupled Magic Trap

“…However, this is much shorter than the dipolar interaction time, preventing observation of many-body spin dynamics.The coherence time in such a magic trap is limited by the intensity dependence of the molecular polarizabil-ity, which originates from the coupling between rotation, nuclear spins, and the trapping light field. It has been suggested to apply large magnetic [28] or electric fields [29] to reduce these couplings and thus simplify the polarizabilities of the involved states.In this work, we realize a spin-decoupled magic trap, i.e. a magic polarization angle trap with moderate dc electric fields, which simplify the hyperfine structure of the rotational transition manifold |J = 0, m J = 0 → |1, 0 .…”

“…The coherence time in such a magic trap is limited by the intensity dependence of the molecular polarizabil-ity, which originates from the coupling between rotation, nuclear spins, and the trapping light field. It has been suggested to apply large magnetic [28] or electric fields [29] to reduce these couplings and thus simplify the polarizabilities of the involved states.…”

Spin-orbit-coupled Bose-Einstein condensates of rotating polar molecules

“…As shown in Ref. [40], under a strong bias magnetic field, e.g., B = B ẑ, M i becomes a good quan- tum number, which can be fixed for instance, by choosing M i = I i . Therefore, the relevant internal states reduce to |N, M N = |0, 0 , |1, 0 , and |1, ±1 at sufficiently low temperatures.…”

“…They are predicted to display interesting quantum phases [37][38][39]. Their counterparts, electric dipolar condensates of molecules with coupling between the rotational and orbital angular momenta [40,41], present an equally promising platform if a SO-like coupling can be identified. Although hyperfine resolved twophoton transfer [6,7] has been realized experimentally, an analogous atomic SO interaction cannot be directly engineered this way because the neighboring rotational levels for rotating molecules possess opposite parities.…”

Coupled spin-vortex pair in dipolar spinor Bose-Einstein condensates

“…Armed with the spontaneous SVS and the tunablity in both the atom-atom interactions and the geometries of the system, dipolar spinor condensates in a multiplewell potential provide an ideal platform for simulating the multilayer magnetic vortices. In particular, the recent successes in creating ultracold gases of polar molecules [38][39][40][41][42][43] offer an opportunities in studying the coupled SVS with higher winding number [44].…”