Excitation spectrum of a toroidal spin-1 Bose-Einstein condensate

Abstract

We calculate analytically the Bogoliubov excitation spectrum of a toroidal spin-1 Bose-Einstein condensate that is subjected to a homogeneous magnetic field and contains vortices with arbitrary winding numbers in the mF = ±1 components of the hyperfine spin. We show that a rotonlike spectrum can be obtained, or an initially stable condensate can be made unstable by adjusting the magnitude of the magnetic field or the trapping frequencies. The structure of the instabilities can be analyzed by measuring the particle densities of the spin components. We confirm the validity of the analytical calculations by numerical simulations.

Persistent currents in coherently coupled Bose-Einstein condensates in a ring trap

“…When the decay in GS1 is driven by the density mode, diagonalization of the full Bogoliubov operator shows that close to instability there appears a roton-like structure that is linked to the nucleation of excitations in the internal surface, similarly to what has been predicted in single components [46] and spinor condensates [47]. This roton-like structure induces a minimum in the Dopplershifted excitation spectrum at finite , which leads to the decay of the persistent current through phase-slips (vortices) when the lowest frequency becomes negative.…”

“…In BECs they have been predicted not only in static situations such as in dipolar condensates [50], but also in the presence of currents in the ground state, such as in spin-orbit coupled condensates [51,52] or the results presented here and in Refs. [46,47]. In the dipolar case, the roton mode touching zero is generally associated to density-wave or supersolid configurations (see the recent experiment [53]).…”

“…( 16). The roton-like structure is not inherent of two-component systems but has been seen to appear as well in single components [46] and spinor F = 1 systems [47]. It has been argued in [46] that it comes from a coupling of the Bogoliubov mode to a surface mode [48,49] localized in the internal surface of the ring.…”

Spin-orbit-coupled spin-1 Bose-Einstein condensates in a toroidal trap: even-petal-number necklacelike state and persistent flow

“…The population imbalance and fixed phase relation between multiple components bring persistent flows novel stability features [18][19][20][21][22]. It has been found that rich phase diagram and interesting collective excitations can exist in interacting two-component [23][24][25][26] and three-component [27][28][29] toroidal BECs.…”

Metastable spin textures and Nambu-Goldstone modes of a ferromagnetic spin-1 Bose-Einstein condensate confined in a ring trap

“…The previous theoretical works regarding multicomponent systems (two-component Bose gases [40][41][42][43][44] and spinor BECs [45,46]) in a ring trap concern the stability of persistent currents. Other important properties, including metastability under external rotation, have also been thoroughly investigated theoretically [47,48] and experimentally [7,8,10] for scalar BECs.…”