Spin-Orbit-Coupled Dipolar Bose-Einstein Condensates

Abstract

We propose an experimental scheme to create spin-orbit coupling in spin-3 Cr atoms using Raman processes. By employing the linear Zeeman effect and optical Stark shift, two spin states within the ground electronic manifold are selected, which results in a pseudo-spin-1/2 model. We further study the ground state structures of a spin-orbit-coupled Cr condensate. We show that, in addition to the stripe structures induced by the spin-orbit coupling, the magnetic dipole-dipole interaction gives rise to the vortex phase, in which a spontaneous spin vortex is formed.PACS numbers: 37.10. Vz, 03.75.Mn Over the past few years, there has been rapidly growing interest in engineering Abelian and non-Abelian artificial gauge fields in ultracold atomic gases [1][2][3][4][5][6]. Particularly, the non-Abelian gauge field, or more specifically the spin-orbit (SO) coupling, is of fundamental importance in many branches of physics. Fascinating examples include the quantum spin-Hall effect and the topological insulators in condensed matter physics [7]. With the enormous tunability of the interaction and geometry, ultracold atomic gases may offer a tremendous opportunity for studying exotic quantum phenomena in many-body systems with SO coupling [8][9][10][11][12][13][14][15][16].In their pioneer experiments, the NIST group have realized the light-induced vector potentials [17], the synthetic magnetic fields [18], and the electric forces [19] in ultracold Rb gases through Raman processes [4], which differs from most dark-state based theoretical proposals [20] in that the linear Zeeman shift is compensated by the two-photon detuning. More remarkably, they also created a two-component SO-coupled condensate of Rb atoms and observed the phase transition from spatially mixed to separated states [21]. An important ingredient in this experiment is that the quadratic Zeeman shift is employed to separate two desired spin states from the remaining one. Hence, this scheme is inapplicable to atoms without nuclear spin, such as certain isotopes of Cr and Dy, in which the quadratic Zeeman effect is absent.In this Letter, we propose an experimental scheme to create SO coupling in spin-3 52 Cr atoms by selecting two internal states from the J = 3 ground electronic manifold. Similar to the NIST group's scheme, ours also relies on Raman processes. However, we utilize the optical Stark shift to compensate the linear Zeeman shift so that the lowest two levels are near degenerate and well separated from other levels, which leads to a pseudo spin-1/2 model. The proposed scheme has the advantages that only a moderate magnetic field strength is required and it also applies to atoms without nuclear spin.An interesting feature of the Cr atom is that it possesses a large magnetic dipole moment, which makes the scalar Cr condensate an important platform for demon- strating the dipolar effects [22]. Moreover, when an atom's spin degree of freedom becomes available, magnetic dipole-dipole interaction (MDDI) also couples the spin and orbital angular momenta, wh...

Collective-mode dynamics in a spin-orbit-coupled Bose-Einstein condensate

“…The coupling between dipole and breathing modes will become significant with larger g 2 , for instance, if similar experiment is done with magnetic atoms like Cr [20], Dy [21] and Er [22]. Nevertheless, even for smaller g 2 , since there exists a window of aspect ratio ω x /ω ⊥ in which the frequency of bare dipole mode is at resonance with one of the breathing modes, as indicated by arrow in Fig.…”

Drag force on a moving impurity in a spin-orbit-coupled Bose-Einstein condensate

“…Although there exists a solution satisfies Eq. (27), it makes f + (k th ) = 0. So there is no jump when the velocity of the impurity reaches v th .…”

“…(27) has θ th − θ 0 = 0. That is, the momentum of the excitation from the upper band at v th is not on the direction of θ 0 .…”

“…It provides physicists with a new platform to study the effects of SOC in many-body systems. A plenty of researches have been done on the properties of the BEC with SOC, including the groundstate phase [14][15][16][17][18][19], fluctuations above the ground state [20][21][22][23], and spin-orbit coupled BECs with other coldatom techniques, such as dipole-dipole interactions, optical lattice and rotating trap [24][25][26][27][28].…”

Momentum-resolved radio-frequency spectroscopy of ultracold atomic Fermi gases in a spin-orbit-coupled lattice

“…The past few years have witnessed an exponential growth of interest in studying ultracold atomic gases under a synthetic gauge field [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The growth is strongly motived by a series of ground-breaking experiments at the National Institute of Standards and Technology (NIST) [1][2][3][4].…”