Bulletin of the American Physical Society
46th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 60, Number 7
Monday–Friday, June 8–12, 2015; Columbus, Ohio
Session P2: Invited Session: Physics of Ultracold Dipoles |
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Chair: John Bohn, JILA and University of Colorado Room: Union ABC |
Thursday, June 11, 2015 2:00PM - 2:30PM |
P2.00001: Ultracold polar molecules in a 3D optical lattice Invited Speaker: Bo Yan Ultracold polar molecules, with their long-range electric dipolar interactions, offer new opportunities for studying quantum magnetism and many-body physics. KRb molecules loaded into a three-dimensional (3D) optical lattice allow one to study such a spin-lattice system in a stable environment without losses arising from chemical reactions. In the case with strong lattice confinement along two directions and a weak lattice potential along the third, we find the loss rate is suppressed by the quantum Zeno effect [1]. In a deep 3D lattice with no tunneling, we observe evidences for spin exchange interactions [2]. We use Ramsey spectroscopy to investigate the spin dynamics. By choosing the appropriate lattice polarizations and implementing a spin echo sequence, the single particle dephasing is largely suppressed, leaving the dipolar exchange interactions as the dominant contribution to the observed dynamics. This is supported by many-body theoretical calculations [3]. While this initial demonstration was done with low lattice fillings, our current experimental efforts are focused on increasing the lattice filling fraction. This will greatly benefit the study of complex many-body dynamics with long-range interactions, such as transport of excitations in an out-of-equilibrium system and spin-orbit coupling in a lattice.\\[4pt] [1] B. Zhu, B. Gadway, M. Foss-Feig, J. Schachenmayer, M. L. Wall, K. R. A. Hazzard, B. Yan, S. A. Moses, J.P. Covey, D. S. Jin, J. Ye, M. Holland, and A. M. Rey. Phys. Rev. Lett. 112 070404(2014).\\[0pt] [2] B. Yan, S. A. Moses, B. Gadway, J. P. Covey, K. R. A. Hazzard, A. M. Rey, D. S. Jin, J. Ye, Nature 501 521 (2013).\\[0pt] [3] K. R. A. Hazzard, B. Gadway, M. Foss-Feig, B. Yan, S. A. Moses, J. P. Covey, N. Yao, M. D. Lukin, J. Ye, D. S. Jin and A. M. Rey. Phys. Rev. Lett. 113 195302(2014). [Preview Abstract] |
Thursday, June 11, 2015 2:30PM - 3:00PM |
P2.00002: Tuning ultracold collisions of excited rotational dipolar molecules Invited Speaker: Goulven Qu\'em\'ener Ultracold molecular dipolar gases often suffer from losses due to chemical reactions (or eventual sticky collisions for non-reactive molecules). Loss suppression for both bosonic and fermionic dipolar species can be obtained in a one-dimensional optical lattice but this requires usually strong confinements to get into a pure two-dimensional collision regime. An alternative way can be found without confinement using rotationally excited molecules. In this talk I will explore the ultracold collisions of rotationally excited dipolar molecules in free space. I will focus on electric dipolar molecules of KRb [1] and electric and magnetic dipolar molecules of RbSr. I will show that we can sharply tune the elastic, inelastic and reactive rate coefficients of lossy molecular collisions when a second rotationally excited colliding channel crosses the threshold of the initial colliding channel, with the help of an applied electric field. We can increase or decrease the loss processes whether the second channel is above or below the initial channel. This could lead to favorable conditions for evaporative cooling. Additionally, we include the electric quadrupole and octopole moment to the dipole moment in the expression of the long-range multipole-multipole interaction. For processes mediated by the incident channel like elastic and loss collisions, the inclusion of quadrupole and octopole moments are not important at ultralow energies. They are important for processes mediated by state-to-state transitions like inelastic collisions.\\[4pt] [1] G. Wang, G. Qu\'em\'ener, submitted to New J. Phys. (arXiv e-prints 1411.7539). [Preview Abstract] |
Thursday, June 11, 2015 3:00PM - 3:30PM |
P2.00003: Photoassociation of long-range $nD$ Rydberg molecules Invited Speaker: Georg Raithel Cold atomic systems have opened new frontiers at the interface of atomic and molecular physics. Of particular interest are a recently discovered class of long-range, homonuclear Rydberg molecules first predicted in~[1] and observed in~[2]. In rubidium, these molecules are formed via low-energy electron scattering of the Rydberg electron from a 5S$_{1/2}$ ground-state atom that is present within the Rydberg atom's volume. The binding mostly arises from S-wave and P-wave triplet scattering. In recent work~[3], we have observed long-range homonuclear diatomic $nD$ Rydberg molecules photoassociated out of an ultracold gas of $^{87}$Rb atoms for principal quantum numbers 34$\le n \le$40. Related results have also been reported in~[4]. The measured ground-state binding energies of $^{87}$Rb$(nD+5S_{1/2})$ molecular states are larger than those of their $^{87}$Rb$(nS+5S_{1/2})$ counterparts, showing the dependence of the molecular bond on the angular momentum of the Rydberg atom. We have exhibited the transition of $^{87}$Rb$(nD+5S_{1/2})$ molecules from a molecular-binding-dominant regime at low $n$ to a fine-structure-dominant regime at high $n$ [akin to Hund's cases (a) and (c), respectively]. In our analysis~[4], we use a Fermi model that includes S-wave and P-wave singlet and triplet scattering, the fine structure coupling of the Rydberg atom and the hyperfine structure coupling of the 5S$_{1/2}$ atom. The hyperfine structure is important because it gives rise to mixed singlet-triplet potentials. \\[4pt] [1] C. H. Greene, A. S. Dickinson, and H. R. Sadeghpour, Phys. Rev. Lett. {\bf 85}, 2458 (2000). \\[0pt] [2] V. Bendkowsky, B. Butscher, J. Nipper, J. P. Shaffer, R. L\"ow, and T. Pfau, Nature {\bf 458}, 1005 (2009).\\[0pt] [3] D. A. Anderson, S. A. Miller, and G. Raithel, Phys. Rev. Lett. {\bf 112}, 163201 (2014).\\[0pt] [4] A. T. Krupp, A. Gaj, J. B. Balewski, P. Ilzh\"oer, S. Hofferberth, R. L\"ow, T. Pfau, M. Kurz, and P. Schmelcher, Phys. Rev. Lett. {\bf 112}, 143008 (2014). \\[0pt] [5] D. A. Anderson, S. A. Miller, and G. Raithel, Phys. Rev. {\bf{A 90}}, 062518 (2014). [Preview Abstract] |
Thursday, June 11, 2015 3:30PM - 4:00PM |
P2.00004: Topological flat bands by dipolar exchange interactions Invited Speaker: Hans Peter B\"uchler We demonstrate the realization of topological band structures by exploiting the intrinsic spin-orbit coupling of dipolar interactions in combination with broken time-reversal symmetry. The system is based on polar molecules trapped in a deep optical lattice, where the dynamics of rotational excitations follows a hopping Hamiltonian which is determined by the dipolar exchange interactions. We find topological bands with Chern number $C=2$ on the square lattice, while a very rich structure of different topological bands appears on the honeycomb lattice. We show that the system is robust against missing molecules. For certain parameters we obtain flat bands, providing a promising candidate for the realization of bosonic fractional Chern insulators. [Preview Abstract] |
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