Synthetic gauge field with highly magnetic lanthanide atoms

Abstract

We present a scheme for generating a synthetic magnetic field and spin-orbit coupling via Raman coupling in highly magnetic lanthanide atoms such as dysprosium. Employing these atoms offer several advantages for realizing strongly correlated states and exotic spinor phases. The large spin and narrow optical transitions of these atoms allow the generation of synthetic magnetic fields an order of magnitude larger than those in the alkalis, but with considerable reduction of the heating rate for equal Raman coupling. The effective hamiltonian of these systems differs from that of the alkalis' by an additional nematic coupling term, which leads to a phase transition in the dressed states as detuning varies. For high-spin condensates, spin-orbit coupling leads to a spatially periodic structure, which is described in Majorana representation by a set of points moving periodically on a unit sphere. We name this a "Majorana spinor helix" in analogy to the persistent spin-1 2 helix observed in electronic systems.In the past few years, several groups have realized a synthetic magnetic field either in traps or in optical lattices [1][2][3][4], and spin-orbit (SO) coupling [5][6][7][8][9][10][11] with alkali atoms. These developments have highlighted intriguing physics in the ultracold atomic gas context. Vortices and the classical Hall effect have been observed with a Bose condensate exposed to a synthetic magnetic field [1,2]. SO-coupling in a Bose gas can lead to superfluid phases with stripe order [12,13] and a rich phase diagram [5,13,14], as well as modify the effective interaction between dressed-state atoms [6]. In addition, SO-coupling also leads to a divergent spin susceptibility, and the magnetic transition it implies has recently been observed [8,15]. Recently, SO-coupled Fermi gases are found to display interesting spin dynamics, topological transitions of Fermi surfaces, and spin-dependent band structure [9,10].However, there are serious challenges with creating exotic quantum matter using the current scheme of generating synthetic gauge fields. The small fine-structure splitting of the excited level used in the Raman-coupling process for alkalis leads to significant heating through spontaneous emission [16]. While lowering the laser intensity will reduce heating, it will also reduce the strength of the synthetic gauge field, pushing the high-field regime of novel correlated physics beyond reach. As of now, the number of vortices generated by synthetic magnetic field is far below that generated by rotations [1].We suggest the use of lanthanide atoms such as Dy [17,18] and Er [19] to overcome these challenges. The particular atomic structure of these atoms-narrow linewidth transitions, large ground-state orbital and spin angular momenta, and large fine-structure splittingoffer many advantages over the alkalis. As we explain later, the narrow-line transitions (2-kHz wide in Dy versus 6 MHz in Rb) and the L > 0 nature of the Dy ground and excited states provide a significant increase in Raman coupling without addit...

Bright solitons in a two-dimensional spin-orbit-coupled dipolar Bose-Einstein condensate

“…In experiments, this type of spin-orbit coupling has been engineered by coupling two hyperfine states of atoms through two counterpropagating Raman laser beams [29][30][31][32][33][34], and such setup could be employed to realize this spin-orbit coupling in Dysprosium [71] with large dipole-dipole interactions. Also, the large magnetic moment in Dysprosium atoms may permit the realization of Rashba spin-orbit coupling [79].…”

“…On the other hand, spin-orbit-coupled BECs with dipole-dipole interactions [70][71][72][73] have also been explored, and intriguing quasicrystals [74] as well as meron states [75] have been found (these ground states are extended and not localized bright solitons). However, whether a soliton can exist in such BECs in 2D with both long-range dipole-dipole interactions and spin-orbit dispersion has not yet been investigated.…”

Chiral currents in one-dimensional fractional quantum Hall states

“…This has been extensively discussed in semiconductor quantum wires with strong Rashba spin-orbit interactions, specifically in the context of helical liquids 11,12 ; when the system is strongly interacting, the possibility of a "fractional helical liquid" was suggested 13 . As an alternative to spin-orbit interactions in electronic systems, effective spin-orbit coupling and Zeeman field may also be generated in systems of ultracold-atoms confined to 1D [14][15][16][17] . Recently, an observation of chiral edge states was achieved using fermionic 18 and bosonic 19 1D gases with an extra synthetic dimension originating from nuclear spin degrees of freedom.…”

Fermionic Suppression of Dipolar Relaxation

“…Rapid heating or population loss are a result of the ensuing spin relaxation and are detrimental to experiments exploring quantum many-body physics or atom chip magnetometry with highly dipolar gases in metastable spin states [16][17][18][19][20][21][22].…”